To know the difference between "boring" or "bored", or "interesting" and "interested", it helps if you know the reasons for the difference. One comes from grammar: the past participle (PP) (VERB+ED/過去分詞) and one comes from the present participle (VERB+ING/現在分詞). So one way to understand the difference is to think about the grammar roots. But there are other ways:

• You can see the difference; 
• You can feel the difference; 
• You can understand the difference;
• You can learn by examples.

See the Difference

The table below shows the two kinds of words: ~ING adjectives and ~ED adjectives. It shows the grammar roots of the words (active and passive) and it has a picture to help you understand.

~ING	~ED
the present participle	the past participle
active	passive
characteristics	feelings

This shows some visual way to see the difference. 

Feel the Difference

If you imagine that something has a power to "terrify", then something that is "terrifying" sends out that power of terror and the thing that gets that power is "terrified".

~ING	power	~ED
Frankie is terrifying!	Terrify! Terrify! Terrify!	I am so terrified!
A terrifying monster!	The power of terror!	A terrified lady!
SEND		GET

You should do the same thing with "boring" and "bored", "confusing" and "confused" and so on. Imagine things that cause those feelings in you.

Understand the Difference

These adjectives all come from verbs: tire; bore; interest; terrify; confuse; surprise ... etc. There are many. When we think about the connection between the verbs and the adjectives (participles) it helps us understand better. Think about the sentence:

"Frankenstein terrifies her." 

Frankie is terrifying!	Terrify! Terrify! Terrify!	I am so terrified!
Frankenstein	terrifies	her.
[Subject]	[Verb]	[Object]
Using the verb shows the connection between the subject and the object. It shows us two sides to the story — the terrifying Frankenstein and the terrified lady. Using a verb means there is some action happening. Frankenstien is doing something to the lady.
Frankie is terrifying!	Terrify! Terrify! Terrify!
Frankenstien is terrifying.
In this case we are thinking about Frankenstein only. He is terrifying. It is his character, or quality. Something that he is, not something that he does. This part of him stands alone. He is terrfying to everyone, not just the lady. This is a strong statement about who Frankenstein is — he cannot change.
	Terrify! Terrify! Terrify!	I am so terrified!
	The lady is terrified.
	Now we look at the other side of the story. How does the lady feel? The lady is the focus. She is terrified. Most of the time we say why, or by what. But the main point is to say how the lady feels. ~ED adjectives describe feelings, so you can only use them to talk about people (and maybe your dog!).

Learn by Examples

If none of the above ways help you, then try to do it with examples. But you have to personalise them. Fill in the blanks. If you are not sure, check your examples with Poligo. Below is a list of some examples to finish. Try to write your own!