Adjectives that end in -ing
Describe the characteristic of a person, a thing or a situation. It CAUSES a feeling.
The books are boring. We are describing a characteristic of these books.
What do these books cause? They make people feel bored.
Adjectives that end in -ed
Describe a feeling or an emotion. It is how we FEEL about something.
He is bored. This is his feeling right now. This feeling was caused by the books.
He is not going to be bored for eternity. He feels bored for now. (it is temporary)
Example Sentences (compare the difference)
l am tired right now. My flight was tiring (because it was a twelve-hour flight).
Public toilets are sometimes disgusting. I am disgusted by the smell of them.
Your speech was inspiring. I'm now inspired to do great things with my life.