Questions about options for uploading first file Thread

I want to upload my first file to ModDB and I have two questions before I do so.

First, I see the following at the bottom of the "Add File" page:

Imgur.com

Can anyone tell me what everything under "Link mods, games, engines, software, hardware, groups" is for and any guidelines for what i should select.

Next, is it possible to edit or replace a file once you have uploaded it?

Help will be greatly appreciated.