How to check out a file.
To check out a file, you do something extra before you edit the file. You place your pointer over the file name, click the down arrow that appears, and then click Check Out. This will reserve the file for only you to work on. People will know that it is reserved for you, because they will see a green check out icon next to the file.
When you’re done, you check the file in, and the check out icon goes away.
There are other details and benefits related to checkout. When you're done with this course, be sure to take the course, "SharePoint document libraries II: All about checkout." The Quick Reference Card at the end of this course provides a link.