The Commits View displays a list of all the commits in the repository sorted by most recently created.
To navigate to the Commits View select Commits from the left sidebar.
Commits have two types of clickable links. The issue number is a unique integer ID given to an issue or a pull request when they are created. Clicking an issue number in the commit message will open a new tab in GitHub and allow you to see the issue or pull request associated (assuming you have permission to the repository containing the issue or pull request).
The SHA (or "hash") is a 40-character unique ID created by GitHub for every commit. Clicking the SHA in a commit will open a new tab in GitHub and display the changes made in this commit.