User Tags are used to tag a keyword to a specific Tender/Project (one could imagine it being like a filing system, the tags are the individual “files” and the search result is the “filing cabinet”):
Default tags and custom tags you have added will be available under User Tags.
You can also tag/untag multiple Projects/Tenders buy using Actions when Search Result is displayed by selecting the tick box on the right hand side of each Project/Tender and clicking Tag/Untag Selection:
A pop up box will open that will allow you to select the relevant tags and then Add/Remove Tags:
Tags can also be added to an individual Project/Tender by opening up the Project/Tender and selecting the “Tags” icon to the left of the page: 
When selecting the “Tags” icon, it will give you a box to type the tag you would like tag the Project/Tender with: 
You select the tick icon
to tag the Project/Tender.
If you would like to Manage your Tags you can do so under Tag Management under Settings. Note: The “Ignore” tag will automatically get added when clicking on the dismiss icon