This is a sample page. It is different from posts because it always stays in the same place and (with most themes) is displayed in the navigation bar. Most people start with an "About Us" page with an introduction for possible visitors to the site. It could say, for example:
Hello! By day I work as a bicycle courier, by night I'm an aspiring actor and this here is my blog. I live in Berlin, have a big dog called Jack, like the Fantastischen Vier and a cold beer.
As a new WordPress user, you should have the Dashboard to delete this page and create a new page with your own content instead. Have fun!