What is the difference between SEM and PPC?

SEM stands for search engine marketing. It is the process of promoting your website in various search engines to build its popularity and reputation. Search engine optimization and social media optimization are two major processes used for search engine marketing.

PPC stands for pay-per-click, a model of internet marketing in which advertisers pay a fee each time one of their ads is clicked. Essentially, it's a way of buying visits to your site, rather than attempting to "earn" those visits organically. Search engine advertising is one of the most popular forms of PPC.