Present participles and past participles used as adjectives

Both present and past participles may be used as adjectives. The present participle always ends in -ing. Past participles usually end in -ed, -d, -en, -n, or -t.

present participles confusing, speaking, boring
past participles confused, spoken, bored

Like all other adjectives, participles can come before nouns; they also can follow linking verbs, in which case they describe the subject of the sentence.

Use a present participle to describe a person or thing causing or stimulating an experience.

The boring lecture put us to sleep. [The lecture caused boredom.]

Use a past participle to describe a person or thing undergoing an experience.

The audience was bored. [The audience experienced boredom.]

Participles that describe emotions or mental states often cause the most confusion.

annoying/annoyed exhausting/exhausted
boring/bored fascinating/fascinated
confusing/confused frightening/frightened
depressing/depressed satisfying/satisfied
exciting/excited surprising/surprised