The Work button lets you access the list of created work items.

40 work

When you click on Work the inbox loads the list of work items that are for me, and it expands the list of other available filters for work items. The button for creating a new work item is also shown.

40 work expanded

Work Inbox

The Work Inbox shows you work items based on the filter you have selected in the expanded list. For example, if the For me filter is selected in the submenu, you will only see work items where you are involved in.

The work items are ordered by Creation date descending, thus showing most recent items first.
40 work inbox