A ‣ Formation 
We form compound nouns by putting two words together (or three) to create a new idea. Compound nouns are very common in English.
Ice hockey is a game of hockey played on ice.
Public transport is transport that can be used by the public.
A campsite is a site for camping. [a place used for a special purpose]
A babysitter is someone who looks after young children when their parents go out.
Income tax is money you pay to the government out of your income [the total amount of money you receive every year from your work and other places].
Your mother tongue is the first language you learn as a child.
A travel agent is someone whose job is to make travel arrangements for you.
A film-maker is someone who makes films for the cinema or television.
A full stop is a punctuation mark at the end of a sentence.
A haircut is the act of cutting someone’s hair, e.g. That boy needs a haircut.
B ‣ One word or two?
Some compound nouns are written as one word, e.g. wheelchair; a few are written with a hyphen, e.g. T-shirt; many are written as two words, e.g. credit card, bus stop. Use a dictionary to check if necessary.
C ‣ Pronunciation 
The main stress is usually on the first part, e.g. 'haircut or 'income tax, but sometimes it is on the second part, e.g. public 'transport, full'stop. Use a dictionary to check if necessary.
D ‣ Forming new compounds 
One part of a compound often forms the basis for a number of compound nouns.
airport e.g. Heathrow
airline e.g. Lufthansa, KLM
aircraft e.g. Airbus A380
bus driver
bus stop
bus station
ID card (identity card)
credit card
birthday card