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:

Hi! 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:

The company XYZ was founded 1971 and since then provides the public with high-quality products. At its location in a small city, the company employs people through 2.000 and supports the city dwellers in many ways.

As a new WordPress user, you should your dashboard to delete this page and create new pages and posts for your website. Have fun!