A terrific thing is something that's amazing or impressive in a good way. You might think of it as the opposite of terrible - instead of being bad, it's wonderful.
When you hear someone call something "terrific", they usually mean it's really great. For example, if your friend loves their new smartphone and says it's terrific for taking pictures, they're saying it's amazing at that particular thing. If a movie is terrific, people probably think it's one of the best they've seen recently. You might also use "terrific" to describe a experience or an event - like going on a super fun vacation would be terrific!
(now rare) Terrifying, causing terror; terrible; sublime, awe-inspiring.
