The communication between forms can be done in the following 3 ways
let say Form A calls FormB

1.Using New_Form: this Terminates Form A and activates Form B

The NewForm will terminates your current active Form A and releases the memory which is used by Form A and Then activates the called Form B.

2.Using Call_Form:
This suspends the Form A and activates Form B.When you close Form B then Form A will active again.
User cant able to navigate between Forms A and B.

3.Using Open Form:
It opens the indicated form B.
User can be able to navigate between forms A and B.
This is used in multi form applications.

The above is just brief on "Functionality".You have to research more when you are implementing.

Regards,
Yugundhar K