What are the similarities between SEO, SEM, SMO, PPC?

As Per my knowledge
SEO means Search Engine Optimization
SEM means Search Engine Marketing
SMO means Social Media Optimization
PPC means Pay Per Click
But, what are the relationships between these nouns?

Your answers are Welcome! Thanks in advance

All working method different but working and result are same

I believe the main aim of all the four is promoting the website and make the website visible to the world.SEO , SMO and PPC are the techniques which are performed under SEM to promote the website.

they all the shape of search engine marketing thanks for this great post

if you read the article about how we do seo for our site and you know all about seo services these all kind of seo and you can say seo techniques