1. A preposition is a word placed before a noun or a pronoun to show its relation to some other words in the sentence.
2. The noun or a pronoun used after a preposition is called its object.
3. A Preposition has no fixed meaning of its own. It derives its meaning from the context in which it is used.

Preposition of Time and Date
(at, on, in, by, to, till/until, during, for, since, from, within, before, after, then)
at: a particular time, a particular age (at 8 o'clock) (at sixteen)
on: a specific date/day (on Monday, on 17th August)
in: a period of time (in the morning, in 1987)
by: before a time (by 8 o'clock)
from: used with to or until e.g. we work from 9 o'clock till 5 o'clock.
during: a period of time e.g. during morning hours.
for: an action which continues for whole period, e.g. I work for eight hours.
since: point of tim, e.g. He has been sleeping since 6 o'clock

Preposition of Place
(at, in, on, to)
at: a small place (village, address, specific places, etc.)
in: a large place (town, city, country etc.)
on: a place of work (not a building)
to: a particular place
in: used for position (stationary position) e.g. (He is in the room)
into: shows motion (he jumped into the river)

Preposition of Movement
(from, to, on, in, by, into, at, off, of, out etc.)
travel by mode of transport : by bus, by air etc.
travel on something : on horse, on foot etc.
from to: one place to another.
at: reaching a specific place
off: (alight) get off a horse, train etc.

Difference between some important prepositions
(1) In and within
'In' means at the end of a given period of time. e.g. She will return in a month.
'Within' means before the end of the given period. e.g. She will return within a month.
(2) Between and among
'Between' refers to two persons or things. e.g. There was a dance competition between Ram and Shyam.
'Among' refers to more than two persons. e.g. The gifts were distributed among the children.
(3) By and With
'By' is used before the doer of an action. e.g. The painting was drawn by Anita.
'With' is used before the name of the instrument with which the action is done. e.g. She drew the lines with a pen.
(4) In and Into
'In' denotes rest. e.g. The dove is in the dove cote.
'Into' denotes movement towards the inside of anything. e.g. He walked into the library.
(5) Beside and Besides
'Beside' means by the side of. e.g. Come and site down beside me.
'Besides' means in addition to. e.g. Besides dancing, he can sing too.
(6) On and Upon
'On' is used for thing at rest. e.g. The dog is on the bed. e.g.
'Upon' is used for things in motion. e.g. The cat jumped upon the table.

Learn and Apply:

Q1. As the cock crowed _________ dawn, I got out of the bed. (on/at)
Answer: at

Q2. If you don't return these books _______ Monday, you'll be fined. (by/on)
Answer: by

Q3. The thief jumped _________ the wall and ran away. (above/over)
Answer: over

Q4. Please take your feet ________ the table (off/down)
Answer: off

Q5. We were at Ladakh ________ 30th August. (since/from)
Answer: since