Description of nullif and isnull in SQL Server

The two functions nullif and isnull in SQL Server are described as follows:

Nullif: two parameters are required.

Example: nullif (A, B)
Note: If a and B are equal, null is returned. If not, A is returned.
Select nullif ('eqeqweqw', '1'). The result is eqeqweqwe.
Select nullif () returns NULL
The types of A and B must be consistent.

Isnull: two parameters are required.

Example: isnull (A, B)
NOTE: If both A and B are null, null is returned. If a is null and B is not null, B is returned. If a is not null and B is null, A is returned, if neither a nor B is null, A is returned.
Select isnull (null, null) returns NULL
The result of select isnull (null, 33) is 33.
Select isnull ('ddd ', null) results in DDD
Select isnull () result is 44