In simple words:
When a page table is too big to fit into one frame, then it gets splitted into more than one frames. Now to keep track of pages of Page Table which are distributed in more than one frames, a separate Page Table is created. This is called as Multi Paging.
2 level paging: In case of Multi paging, when 2nd page table size fits into Frame size, then its 2 level paging. No more page tables are generated as complete Page Table gets fit into one single frame.
For more details: https://www.geeksforgeeks.org/operating-system-paging/
