Learning about Parameters
Parameters are variables that being passed to a Sub.

Look at the first line of the Command Button's Click event:

Private Sub Command1_Click()

And at the first line of the Command Button's KeyPress event:

Private Sub Command1_KeyPress(KeyAscii As Integer)


The Click event's first line is ended with
empty parentheses   ()   and the KeyPress event's first
line is ended with  (KeyAscii As Integer)


What is the   (KeyAscii As Integer)   ?
It's a parameter that been passed to the KeyPress event.

This parameter is an Integer variable with the name KeyAscii.
Like if you've declared     Dim KeyAscii As Integer

Why do we need this variable?
Because its value is very useful.

The KeyPress event is being executed when the user
press a key, and This variable holds the Ascii value of the
key that been pressed.
With This Ascii value you can know on which key
the user has pressed.

For example, the Ascii value of the "A" character is 65.
If the user has pressed the key "A" on the keyboard,
The KeyAscii parameter value will be 65.

Lets see an example.
Insert the following line to the Command1 KeyPress event:

Private Sub Command1_KeyPress(KeyAscii As Integer)
    Print KeyAscii
End Sub