SEO Basic concepts

 1. Search engines

Before we start talking about search engine optimization we need to understand how search engines work. Basically, each search engine consists of 3 parts:

1. The Crawler (or the spider). This part of a search engine is a simple robot that downloads pages of a website and crawls them for links. Then, it opens and downloads each of those links to crawl (spider) them too. The crawler visits websites periodically to find the changes in their content and modify their rankings accordingly. Depending on the quality of a website and the frequency of its content updates this may happen from say once per month up to several times a day for a high popularity news sites.
   
   The crawler does not rank websites itself. Instead, it simply passes all crawled websites to another search engine module called the indexer.
2. The Indexer. This module stores all the pages crawled by the spider in a large database called the index. Think of it as the index in a paper book: you find a word and see which pages mention this word. The index is not static, it updates every time the crawler finds a new page or re-crawls the one already presented in the index. Since the volume of the index is very large it often takes time to commit all the changes into the database. So one may say that a website has been crawled, but not yet indexed.
   
   Once the website with all its content is added to the index, the third part of the search engine begins to work.
3. The ranker (or search engine software). This part interacts with user and asks for a search query. Then it sifts millions of indexed pages and finds all of them that are relevant to that query. The results get sorted by relevance and finally are shown to a user.

2. Terminology

Here are the basic terms you need to know. All others will be explained along the way. 

Anchor text
This is simply a text of a link. Let suppose you have a link like that:

The essentials of SEO - a complete guide
The link would be looking as follows:
The essentials of SEO - a complete guide

The text "The essentials of SEO - a complete guide" - is the anchor text in this case. The anchor text is the key parameter in a link building strategy. You should always make sure that the anchor text of a link meets the theme of that page. If your page is about dogs, do not link to it with the "cats" anchor text. Obviously, you cannot control all and every link on the web, but at least you should make all links within your own website have an appropriate anchor text.

Inbound link
...or backlink is a link that points to your site. The more you have - the better. But in particular there are many exclusions from this rule, so read the Off-Page optimization section to learn more.

Keyword
One or more words describing the theme of a website or page. In fact, we should distinguish keyWORDS and keyPHRASES, but in SEO practice they all called keywords. For instance, the keywords for this page are: SEO FAQ, SEO tutorial, etc.

Short-tail and long-tail keywords
Easy one. Short-tail keywords are some general, common words and phrases like "rent a car", "seo", "buy a toy", "personal loan" and so on. Long-tail on the opposite precisely describe a theme: "rent bmw new york", "seo in florida", "buy a plush teddy bear" etc. The more precise a keyword is, the less it is popular, the less people type this exact query in the search box. But! The other side of the coin is: since each query is highly targeted, then once a visitor comes to your website from a search engine query and finds what he is looking for - it is very likely that such visitor will soon become a customer. This part is very important! Long-tail queries are not very popular, but the conversion rate for such queries is much much greater than for short-tail ones.

SERPs
You may heard this term, but didn't understand what is it. SERP means "Search Engine Result Page". If a user types some query and hit Enter he is redirected then to a SERP. Then he can click one of the results to open that website. Obviously, the results shown in the first positions get much more visitors than the ones from page #2-3 and lower. This is the purpose of SEO, actually: make a website move higher in SERPs.

Snippet
This is a short description shown by a search engine in the SERP listings. The snippet is often taken from a Meta Description tag, or it can be created by a search engine automatically basing on the content of a page. 

Landing page
Landing page is a page opened when a visitor comes to the site clicking to a SERP. Here is an example query:


In this case, the page www.cleverstat.com/en/google-monitor-query.htm is a landing page for the "google monitor" query. 

Link juice
This funny term means the value that passes from one page to another by means of a link between them. To be precise: the linked page (acceptor) gets a link juice from the linking page (donor). The more link juice flows into a page, the higher it is ranked. Let's imagine a page that is worth $10 - this is the value of that page. If a page has 2 links, each one costs $5 then - that is the amount of link juice passed to the linked page. If the first page has 5 links, then each one only passes $2 of the initial link juice. Here is a simple picture to illustrate this concept:



Each link passes $5 value


Each link passes only $2 value

This means, the more links a Page A has, the less value each linked Page B gains from that Page A. Obviously, the real link juice value is not measured in dollars.

Nofollow links
Nofollow link is a link that a search engine should not follow. To make a link nofollow you need the below code:

Some anchor text

Google does not follow nofollow links and does not transfer the link juice across such links. You can read more about nofollow links here. 

Link popularity
This term designates the amount of inbound links pointing to a site. Popular sites have more links. However, the number of inbound links is only a half of a pie.

Keyword stuffing
When you put a long list of keywords in a tag - this is keyword stuffing. For instance, a title tag for this page could look like:and so on. This would be the keyword stuffing. Instead, the current title of this page (the one you're reading now) looks quite natural and adequately describes its contents. Do not use the keyword stuffing as a) it does not work; b) it is a bad practice that can hurt your rankings.

Robots.txt
robots.txt is a file intended to tell search engine spiders whether or not they are allowed to crawl the content of the site. It is a simple txt file placed in the root folder of your website. Here are some examples:

This one blocks the entire site for GoogleBot:
User-agent: Googlebot
Disallow: /
This one blocks all files withing a single folder except myfile.html for all crawlers:
User-agent: *
Disallow: /folder1/
Allow: /folder1/myfile.html