Pagerank: Pagerank is google algorithm to estimate the relative important of web pages around the web. The basic idea behind Pagerank algorithm is the fact that a link from page A to page B can be seen as a vote of trust from page A to page B. The higher the number of links (weighted to their value) to a web page, therefore, the higher the probability that such page is important.
SEM : SEM Stands for Search Engine Marketing, It involves marketing services or products via search engines. SEM is divided into two main pillars called SEO and PPC. Seo stands for Search Engine Optimization, and it is the practice of optimizing websites to make their web pages appear in the organic search results. PPC stands for Pay-Per-Click, and it is the practice of purchasing clicks from search engines. The clicks come from sponsored listings in the search results.
Backlinks: Backlinks are also called as inlink or simply link; it is a hyperlink on another website pointing back to your own website. Backlinks are important for SEO because they affect directly the PageRank of any web page, influencing its search rankings.
Link Farm: Link farm is a technique where a group of websites link with every other website with the purpose of artificially increasing the PageRank of all the sites in the farm. This practice was effective in the early days of search engines, but today they are seeing as a spamming technique (and thus can get you penalized by Search engines).
Linkbait: Linkbait is a piece of web content published on a website or blog with the goal of attracting as many backlinks as possible (in order to improve one’s search rankings). Usually it’s a written piece, but it can also be a video, a picture, a quiz or anything else. A classic example of linkbait is the “Top 10″ lists that tend to become popular on social Bookmarking web sites.
SERP: Stands for Search Engine Results Page. It’s basically the web page you’ll get when you search for a specific keyword on Google or on other search engines. The amount of search traffic your website will receive depends on the rankings it will have inside the SERPs.