To blog or not to blog

I'm feeling like I want a website and a Blog is the obvious option.... however I don't really understand why people blog.

In Kenya it was a wonderful way of keeping in touch with many people I know. However some people use blogs as a rather personal journal which I find odd..
How am I meant to respond to their pains and happiness?
Do I admitt that I know their innermost thoughts or is this something you can read and not talk about it?
If someone is angry with me in a blog does this mean I should see it as being told off or should I wait for them to approach me?

it's all very odd...
I think I want a website rather than a blog but I'm not very web design literate so not sure how yet....