This is your homepage. It is different from a blog post because it will stay in one place and will appear in the navigation of your site (in most themes).
Once you are logged into WordPress, you can edit this page by clicking the Edit Page button in the toolbar. This page can be used to introduce yourself or your company to potential visitors to the site and might say something like this:
Bye! I'm a bike messenger by day, aspiring actor by night and this is my website. I live in Los Angeles, I have a big dog named Jack and I like piña coladas. (And take the rain)
.... or something like that:
The company XYZ Aggeggi was founded in 1971 and since then has been supplying the public with top quality gadgets. Located in Fantasilandia, XYZ employs over 2,000 people and makes all sorts of fantastic gadgets for the Fantasilandia community.
If you would like a list of the most recent articles to be displayed on your homepage, go to Settings and select the option "Latest articles".
Have fun!