Search Engine Marketing (SEM) is one of the most important type of Digital Marketing activities. It helps businesses gain market online with the help of Ads on search engines such as Google (Google Ads), Bing or Yahoo. 

SEM helps in optimizing and hence increasing the brand presence for businesses with the help of paid and unpaid advertising.

Unpaid SEM is called SEO while Paid SEM is called PPC.

PPC (Pay-Per-Click) is a type of Digital Marketing Channel that helps to drive traffic to the website. PPC is a paid form of marketing which involves buying traffic through paid search listings. This allows the marketers to drive more web traffic.

There are various terms related to Search Engine Marketing such as Paid search ads, Paid search advertising, PPC (pay-per-click), PPC (pay-per-call), CPC (cost-per-click), and CPM (cost-per-thousand impressions).

PPC campaigns are usually set by Adword experts who design campaigns for paid marketing.

SEO on the other hand does not involve any form of paid campaigns.