The reference log (RefLog) displays the history of a reference (i.e., it is displayed to which commits it pointed in the past). It can be opened using Shift key while right clicking on on a folder in the explorer in order to see this, because it is in the extended context menu by default.→ , however, you have to hold the
The RefLog can be used to restore deleted commits or HEAD positions (e.g. when you deleted a branch which was HEAD some time ago).
You can find more information at git-reflog(1) man-page.