dot and underscore characters

Hello,
When looking for help on how to use EditText the following questions came up to me:
I understand that dot is used for working down on the properties of an object
like

EditText1.Text.Trim.Length = 0

Click to expand...

But then I see that EditText1 is followed by an underscore character

Sub EditText_FocusChanged (HasFocus As Boolean)

Click to expand...

(examples from EditText - Basic4android Wiki). So, should the second quote read EditText1_.... instead of EditText?

A question is also: Is there restriction to use dot and underscore characters in naming objects?

Thanks for answer.
positrom2