I'm confused between SEO and SEM?

As a beginner in an online business, I only know a little about web marketing or rather making my business get more followers. I've been hearing about seo and sem and even used the terms interchangeably. But, I know they can both help boost my clothing online site's popularity. I'm confused between SEO and SEM? I want to know if both are reliable and do I need someone to do it for my website? I want to learn more.

google.

this isnt some business fourm ;)/>

http://blog.hubspot.com/insiders/seo-sem-faqs

Sorry, just don't know where to ask this question. I have been searching online the whole day to further understand these SEM and SEO. I found their brief and concise meaning which was almost similar to what you found. I think this would also help other beginners.

SEM- Paid search

SEO-is strategies, techniques and tactics to increase the number of visitors to a website by obtaining a high-ranking placement in search results

Just sharing. TY

Please don't share those sort of links here. They'll only attract the sort of traffic we don't want. :)/>