A lot of adjectives are made from verbs by adding -ing or -ed:
The commonest -ing adjectives are:
If you call something interesting you mean it interests you.
If you call something frightening you mean it frightens you.
I read a very interesting article in the newspaper today.
That Dracula film was absolutely terrifying.
The commonest –ed adjectives are:
If something annoys you, you can say you feel annoyed. If something interests you, you can say you are interested.
The children had nothing to do. They were bored.