Let’s take a look at some of them.

Algorithm – A system that a search engine uses to rank the web pages in its index, for a certain query. The working of an Algorithm is kept a secret.
Back links – Direct links to your websites through other sites. This is called Off-page optimization of Search Engine Optimization.
Banned – Removal of pages from the index, if they are found to be violating the rules like spamming.
Click-through Rate – Out of the people who saw the link, how many actually clicked and visited it.
Cloaking – Showing a completely different content to the spiders from what the visitors would see.
Conversion rate – Number of visitors that are converted into clients.
Cost per click (CPC) – The advertiser pays an amount for every click he receives on the link leading to his website.
Cost per mille (CPM) – The advertiser pays an amount for every thousand times his ad is flashed on the site.
Crawler – An element of a search engine that crawls on the web to collect listings, travels link by link to understand the connectivity of the pages.
De-listing – Removal of pages from the index of a search engine because they have not been updated for a long time.
Directories – A search engine where the listings are collected by humans, and not by automated web crawlers.
Index – Collection of information in the search engine.
Listings – The list of result that appears on the result page a search engine.
Search Engine Optimization works towards getting your site on top of the listing.
Meta-search engine – Search engine that brings up listing from other search engines rather than from its own index.
Meta tags – Tags that help the search engine understand the contents of a site. Putting correct Meta tags is called on-page optimization in Search Engine Optimization.
Meta robots tag – Does not allow a webpage to be listed.
Natural listings – The listings where an advertiser does not pay to be listed.
Paid placement – An advertiser pays to get a higher listing
Rank – The order of the listings in search engine results.
Reciprocal link – Exchanging links with another site.
Search engine – A service where users get the sites in which information regarding their query is stored.

Search Engine Optimization (SEO): Enhancing a website so that it appears at the top of the listings, of a search engine.
Spam – Any marketing method that is detrimental to the delivery of relevant search results.
Spider – Same as Crawler.
Submission – Sending of a URL to be included in the index of a search engine.

Knowing the terms used in a Search Engine Optimization the task of understanding the process becomes easier.