Clarify why you'd use a fork (github#26153)

Author: hubwriter

content/get-started/quickstart/fork-a-repo.md

@@ -21,7 +21,7 @@ topics:
 ---
 ## About forks
 
-Most commonly, forks are used to either propose changes to someone else's project or to use someone else's project as a starting point for your own idea. You can fork a repository to create a copy of the repository and make changes without affecting the upstream repository. For more information, see "[Working with forks](/github/collaborating-with-issues-and-pull-requests/working-with-forks)."
+Most commonly, forks are used to either propose changes to someone else's project to which you don't have write access, or to use someone else's project as a starting point for your own idea. You can fork a repository to create a copy of the repository and make changes without affecting the upstream repository. For more information, see "[Working with forks](/github/collaborating-with-issues-and-pull-requests/working-with-forks)."
 
 ### Propose changes to someone else's project