With Team Foundation Server you can either remove a Work Item by changing its state (leaving it on the backlog then, not really a removal) or permanently destroy it. No middle ground, no real choice if you need to clear the backlog.
With Visual Studio Team Services instead you have this middle ground, with the Recycle Bin.
It is literally that – you can now delete a Work Item via the context menu and it would be gone, moved to the Bin. Pretty much like a file.
Of course it isn’t actually destroyed (only witadmin destroywi can do that, and it needs confirmation for doing that), but it is only hidden from the backlog. All the traceability is retained, which is very handy.