This is a sample page. It differs from posts because it always stays in the same place and (for most themes) it is displayed in the website navigation. Most start with an imprint, the data protection declaration or an „About us“ page to introduce themselves to potential visitors to the website. For example, there could be:
Hello! During the day I work as a bike courier, at night I am an aspiring actor and this is my website. I live in Berlin, have a big dog named Jack, I like piña coladas, but I don’t like being left out in the rain (without an umbrella).
… or something like this:
XYZ was founded in 1971 and has been providing the public with high quality products ever since. At its location in a small city, the company employs over 2,000 people and supports city residents in many ways.
As a new WordPress user, you should go to your dashboard to delete this page and create new pages and posts for your website. Have fun!