Check In/Check Out the document, which helps the team in a collaborative environment to manage the files. It allows only one person to work on a file at a time, to prevent team members from overwriting each other's changes.
Check-Out : Checking out a file means that you are locking it for editing.This allows you to work on a file without worrying about others modifying it. Also, it will show who has the file checked out. That way, everybody knows who is working on it.
Check-In : Checking-In a file means that you are uploading the modified file to the document management system and it is now available for edit by other shared users. This is done after you have checked it out and made your changes. You can comment what changes you made to it, when you check it back in. Then, other shared users can see the history of changes made to the document.