Do I or Do I not,... need a blog?

If everyone else has one,... Do I need a blog? Is it easy to add it to my site? How often do I have to blog? Just how do they get those pics and videos, on the page? WordPress, Blogger, and the list goes on,... what is the difference? Where is it hosted? How do you get someone to look at? Bottom line,... How much does it cost?