Locked posts can't be: Edited, Voted on, Commented on, Answered, nor Flagged with most flags. Use this for questions with how the API handles such posts, or for tools/apps/scripts that deal with locked posts.
Locked posts can't be:
- Voted on,
- Commented on,
- Answered (if the post is a question),
- Flagged with most flags. ("In need of moderator intervention" flags are sometimes still allowed.)
In general, locks are used whenever modifications to a post are causing serious problems on the site. See the reference(s) below.