1. sb is interested in sth.某人对某事感兴趣.符合常规的：“人用-ed”
2. sb. is interesting某人是有趣的,不符合常规用法,但跟“某物是有趣的”是一种用法：

Tom is interested in sports.Tom对运动感兴趣.
Tim is an interesting guy. Tim是个有趣的人.

希望对你有帮助