User:Laineethecat/sandbox

So, I clicked on "Sandbox" and this page came up. I got this message at the top: "Wikipedia does not have a user page with this exact title. Before creating this page, please see Help:Subpages. " I clicked on the link. I have no idea what this is, or what the Help:Subpages page is all about.

Also, I got this message: "To start a page called User:Laineethecat/sandbox, type in the box below. When you are done, preview the page to check for errors and then save it."

So I did, and here we are. What now, I wonder.