Can someone explain google adsense to me

Tweet

Ive read up about it and Im getting a bit confused. I have just started a blog and am waiting for my adsense account to be verified. When I am able to use it do I post the ads on there or does google provide them? Also I have read different things about adsense and ptc's, I do a few ptcs so it would be nice if I could post the links on my blog, however someone mentioned somewhere that you cant post ptc links with google adsense on your blog. Someone else said that you cant post your blog link on any ptc site. Which one is correct? Are they both right? Thank you to anyone who can help me!