►Describes an action you are doing.

Most commonly, you would use the word 'in' when entering a physical location or you are in a physical location such as a room or a building.

Here are some examples:

1. I am in the shower.
2. I am in the lobby.
3. I was in the lobby.
4. He was in the shower.
5. He is in a car.
6. He is in a house.
7. They are in a school.

♦Using the word 'at' helps tell someone where you currently are. The difference between 'at' and 'in' is that the physical location is general.

Here are some examples:

1. I am at the grocery.
2. I am at the mall.
3. I am at the doctor's office.
4. He is at the park.
5. They are at the airport.

♦However, in some cases you can use 'at' and 'in' interchangeably.

Here are some examples:

1. I am at the mall.
2. I am in the mall.
3. He is at the park.
4. He was in the park.
5. I am at the grocery.
6. I am in the grocery.

♦Using the word 'on' is referring to a non physical location such as your time being utilized by something else.

Here are some examples:

1. I am on the phone.
2. I am on my computer.
3. I am on a bus.
4. He is on computer.