These are all prepositions. Prepositions such as "In", "At and "On" are words used to indicate location and time.
I am waiting at the bus stop. (Specific place)
I was dining in the mall. (Within a specific place)
I reside in San Francisco. (Within an area)
Your eraser is in your drawer. (Inside an enclosed place.)
You look silly standing on the rooftop.(Supported by a surface)
The meeting will start at 3 pm. (A specific time)
The flight is scheduled to land in two hours' time. (Within a time frame)
Janet was born in 1996. (Event that took place in a particular year.)
Music lessons are held on Fridays. (Event that takes place on a certain day of the week)
The summer season starts in July. (Event that takes place in a certain month of the year)
I hope this helps.