Can somebody explain the use of NOT and its Syntex?

Question

from examples I learned NOT is used before condition. not inside the condition. and it's used to make a condition negative.

Answer 1

select customer_name from where city not in ('Tokyo',La') this will give the answer that customer_name which are not from Tokyo or La

Answer 2

select * from tableA where column1 not in (1,2,3)