What is the difference between logical statements and statement variables? For the following two question
Let P, Q, and R be logical statements. Use a truth table to prove that_______.
Let P, Q, and R be statement variables, and suppose that the logical expression_______ is false.
The blank is two expressions which I don't know how to type those symbols, hope it doesn't matter.

A logical statement like $P$ is meant to be a specific statement. For example, $P$ could mean 'It is raining'.
A statement variable is something we use to indicate that we are dealing with some statement ... but we don't know what it is.
It is like the difference between $2$ and $x$ when doing algebra. The $2$ is a specific number, but the $x$ is some unknown number.
