:tabnew, gt, gT โ tabs are layouts of windows, not files.
Keys: :tabnew, gt, gT
:tabnew creates a new tab. gt cycles forward; gT backward. Each tab can have its own arrangement of splits. Most users don't need tabs at all.
Vim's tabs are not what tabs mean in other editors. In Vim, a tab is a layout of windows โ a saved arrangement of splits. The same buffer can appear in multiple tabs; closing a tab doesn't close the buffers it showed.