What is the difference between a lock and a latch in the context of concurrent access to a database?

Question

I am trying to understand a paper on concurrent B-tree, in which the author mentioned latch vs lock, and how latches do not need a \"Lock Manager\". I have been trying to figure

Answer 1

Locks can be added on database entities, e.g. tuples, transactions.

Latches can be added on underlined data representation, e.g. page table in memory which maps page identifier to a specific frame.