Difference between SEO and SEM

SEO
SEO is known as Search Engine Optimization and it is related to using some optimized techniques to get better rankings in the search engines. It is used for getting free traffic form search engines. You optimize the
content of your website according to the policies of search engines thus making your website rank at the top. When users searches a query and your website is at the top, they open your website for getting the
information. This increases the traffic of your website.
SEM
SEM which is called as Search Engine Marketing includes methods of advertising the products and services of your website on search engines using various paid campaigns. It is done to get more and more visibility in search engines by creating an ad and paying for it to search engines so that they can display it at the top of the page. This increases the popularity of your website and people who are in search of some reliable product or service get directed to your website when they click on the ad.
Difference between SEO and SEM
The major difference between Search Engine Optimization and Search Engine Marketing is the fact that SEO is a part of SEM. Search Engine Marketing is categorized above SEO and it basically includes several techniques of Search Engine Optimization. With the help of paid advertising in SEM, you manage to get advertising space in search engines.
Most of the time, people use search engines to get a solution of their problem. So, when they click an ad or a website from search results, they usually convert into customers. That is why, the SEM traffic is considered as the most important traffic of internet as it is targeted and hold high potential of converting visitors into customers.