Excuse me: What is the function of this sentence?

Excuse me: What is the function of this sentence? Delphi/Windows SDK/API
Http://www.delphi2007.net/DelphiBase/html/delphi_20061207130246245.html
A Program There are the following operations on window fmxx:
If not assigned (fmxx) then
Fmxx: = tfmxx. Create (Self) // (1) What is the function of this sentence?

Else
Exit;
Fmxx. show;

_____________________; // (2) what is required to release the occupied resources?
Fmxx: = NULL;

A program has the following operations on window fmxx:
If not assigned (fmxx) then
Fmxx: = tfmxx. Create (Self) // (1) What is the function of this sentence?

A: This is an instance for creating a class.
Fmxx: Class variable.
Tfrmxx. Create (Self); this is the class constructor. The parameter is the owner of the current instance. The owner is responsible for managing the memory space of the current instance.

Else
Exit;
Fmxx. show;

Fmxx. Free; // (2) what resources are required to be released here?
Fmxx: = NULL;

Thank you.