To collect something is to get or gather it and then keep it for some purpose. This forms a collection. There are many different things that people collect:
Ron collects coins. He has a coin collection. (The word "collection" is a noun.)
Tammy likes to collect dolls. She has a doll collection.
When I was a boy, I collected comic books. Now I like to collect old radios.
Many people in the United States collect antiques. As the antiques age, they become more valuable.
Is there anything that you like to collect?
The word "collect" is often used when taking money for the benefit of a person or a group of people:
We’re collecting money for Sarah’s family. Her father died.
The Salvation Army collects money during the holidays to help people who are poor.
Tolls are collected at tollbooths in the United States to pay for highway construction.
The IRS collects money from U.S. taxpayers.
You can also use "collect" when an amount of something increases over time:
Dust is collecting on top of the TV set.
Garbage collected in the streets when the sanitation workers went on strike.
Several inches of snow collected on the highway overnight.
There’s a collection of boxes and cardboard that the store needs to get rid of.
The word "collectible" is an adjective. If something is "collectible," it’s a good thing to collect or it’s easy to collect:
Those little ceramic figures are very collectible.
Certain cars are considered to be collectible, but cars are expensive things to collect.
The word "collector" is a noun that is used for people who collect things:
Ron is a coin collector.
Tammy is a collector of old dolls.
Car collectors value cars that have original parts.
Tax collectors make sure that everyone pays taxes.
Note: Before cell phones, it was common for people to make a "collect call." This was a phone call made from a pay phone. If you didn’t have the money to pay for the call, you would speak to a telephone operator who then contacted the person for whom the call was intended. The operator would then ask the person receiving the call if he or she would pay for it. Collect calls are rare now, but they are still made.