SAT stands for boolean satisfiability. You have variables that can be true or false. You have constraints called clauses that must all be satisfied. A clause is an OR statement: "a OR b OR c must be true." You need at least one of them to be true.
Your goal: pick true or false for each variable so every single clause is satisfied. If that is possible, the formula is satisfiable. If no assignment works, it is unsatisfiable. General SAT with arbitrary clause sizes is NP-complete, meaning no known fast algorithm exists.