This question already has an answer here:
A formula is valid if it is true for all values of its terms. Satisfiability refers to the existence of a combination of values to make the expression true. So in short, a proposition is satisfiable if there is at least one true result in its truth table, valid if all values it returns in the truth table are true.
Even given these definitions it is still not clear to me what sentences are valid or not.
What are some examples of sentences that are valid or (un)satisfiable?