Simply, editing means changing.

Anyone with less than 2000 reputation can suggest a change to your post. You can approve or reject that. Anyone with more than 2000 reputation can unilaterally change a post without any approval process. People with more than 2000 reputation also will approve the edits made by people with less than 2000. It takes two people approving it to be approved. 

You can see the edits by clicking the link "edited X" (e.g. "edited yesterday") above the photo of the most recent editor. This gives you an edit history:

[![][1]][3]

Here we can see 

If you disagree with the edits because they changed the meaning of your post you can edit them back. It's your post. However, don't keep doing this - if they make their edit again, come here ([meta.askubuntu.com][2]) and ask a question about it!

If you just want to discuss an answer, you can add a comment below your post which starts with `@username` - for example, if I comment below this question `@pomsky`, pomsky will get a notification. This works for anyone in the edit history!

  [1]: https://i.sstatic.net/T3h98.png
  [2]: https://meta.askubuntu.com
  [3]: https://askubuntu.com/posts/1030796/revisions