Version Control Check In dialog

Recursive
Check in items subordinate to the selected item.
Keep checked out
Checks in the current version of the item but keeps it checked out to you.
Check in items checked out by others
Checks in items that are checked out by other users. Other user's changes are checked in. Once checked in, the item is available to be checked out again.
Comment
Enter a comment to describe the changes made in this version
Differences
Compares the item you are checking in with the most recent previous version. This can help you enter a meaningful comment.