Definition
A preposition is a word or groups of words used before a noun or a pronoun to show place, position, time or method. A preposition can have many usage.

Here are some preposition and some of their usages:

• Preposition In: use 'in' with periods of times and places

Examples:-month: in March
-season: in winter
-country: in Indonesia
-city or town names: in Palangka Raya
-times of the day: in the morning

• Preposition On: use 'on' with specific days.

Example:
on Saturday, on New Year's Day, on March 20, on the weekend

• Preposition At: use 'at' with specific time and place

Example:
at school, at 7 O'clock, at night