Adjectives are words that describe nouns, such as a person, place, or thing.   They can also have different endings, such as -ed or -ing.  One or more can be used at one time, but they must be in a certain order (more about that later!).

So let's start with some examples of adjectives:

bored, boring
tired, tiring

excited, exciting

fun, funny

pretty

horrible

interested, interesting

Adjectives ending with an -ed should only be used for people or living things.  You can say "My dog is tired," but not "My book is tired."  On the other hand, if you want to say that your dog is making you run around too much or play too much with him, then you can say "My dog is tiring."  This means your dog is making you feel tired.  You can also say "I am excited," but "This book is exciting."  You feel excitement and the book makes you feel excitement.  The book cannot be excited or tired because it is an inanimate object and not alive.

Now we can talk about adjectives ending in -ing.  These are used to describe things, events, or activities.  We can say "I had an boring day," or "That lecture was interesting," but not "I was boring today," or "That lecture made me interesting."  Your day and the lecture are not alive (plus it's bad to call yourself boring...others can but you hopefully don't feel that way about yourself!), so they can only be used with -ing adjectives.

Here's some more examples to help you remember all that:

I am bored. / The lecture was boring.  (you are a person, so you can feel bored, whereas the lecture is not alive, so it can just be boring to people)

Carlos is disappointed by the news. / Andy's test results were disappointing to his parents. (Carlos feels disappointed because he is a person, whereas Andy's test results are a thing, so they are disappointing)

My mother was shocked when I told her I was getting married to a famous actor. / The news about her winning the lottery was shocking to everyone. (My mother felt shocked because she is a person, whereas the news about her winning the lottery was shocking because it is a thing and not alive)