Adding tags to users and products ensures that users only work on pickings with matching tags. This can be useful if users need to fulfil certain criteria, e.g. having knowledge about dangerous goods.
First make sure, that affected users and products are tagged correctly - both need to have the same tag(s). See this article on how to set tags.
Whenever a user now tries to accept a picking that contains products which do not match her tags, the following message ist shown:
It is also possible to only display those pickings to a user which match her tags. To activate this setting go to menu item Settings and activate Filter picking list based on product tags (1).