Within Administration > HR > Data management > Recruitment you will find a new option called Requisition Categories.

From here you can add your own requisition categories which can then be assigned to each of your new or existing requisitions within the Recruitment module. 

When adding / editing a requisition you will now see a new field called 'Requisition category'. From here you will be able to select one of the categories from the list you created.

If you no longer require a particular requisition category, you can use the bulk actions on the Requisition categories page to archive it. Doing this will remove that category option from the list on the Requisitions page.