The prepositions "at, in and on" are primarily prepositions of: * place/location * time * direction However, there are other uses for these pronouns, as described below: At 1. A specific location:.....at 23 Chestnut Street; at the park 2. A point in time:...........at 5 o'clock; at Christmas 3. A condition:................at peace; at war; at rest 4. An activity:.................at work; at school; at play 5. Towards:....................Look at someone; wave at someone Note: When referring to a specific location or to a point in time, “at” is usually used. When referring to a certain street or a certain day, “on” is usually used. When referring to a location as an area, or when referring to a unit of time longer than a day, “in” is usually used. e.g. at Christmas; on Christmas day; in the Christmas holidays In 1. Place thought of as an area:.....in London / in Europe 2. Within a location:.....................in the room / in the building 3. Large units of time:..................That happened in March / in 1992. 4. Within a certain time:...............I will return in an hour. 5. By means of:..........................write in pencil / speak in English 6. Condition:...............................in doubt / in a hurry / in secret 7. A member of:..........................He is in the orchestra / in the navy 8. Wearing:.................................the boy in the blue shirt 9. With reference to:....................lacking in ideas / rich in oil On 1. Touching the surface of:.....on the table / on the wall 2. A certain day:....................That happened on Sunday / on the 6th of June. 3. A certain street:.................on South Street/the store on Main Street 4. About:...............................a book on engineering/a TV show on travel 5. A state or condition:...........on strike / on fire / on holiday 6. By means of:.....................live on a pension / shown on television

"At" is a point which you meet. It suggests there is some kind of transit happening. "In" is a place which exists within limitations (eg. walls, borders, and so on). It doesn't move.

At and in have very similar meanings depending on the context. The biggest differences is that with in, you are usually saying you are inside. For example, you are in your house means you have gone through the door and are no longer outside. However, if you are at your house you could be inside, but you could also just be near your house, maybe just outside the door. There are other uses where things get a bit more complicated but that is the main one you need to know about. :)