syntax for expressions

[Willard Bertrand]

Please provide explanation of the following syntax, using
examples where possible:

"tablename.fieldname"
(tablename.fieldname)
"txtstring"
(txtstring)
'forms!form.txtbox.value'
"'forms!form.txtbox.value'"
"forms!form.txtbox.value"
"john''s"

I am trying to get this parenthesis, single quote, and
double quote syntax clear to use in SQL, as an object's
property values, or in queries.

Thank you.

Willard