What is Baggage Allowance?

Legal Definition
On the commercial transportation, mostly with airlines, the baggage allowance is the amount of checked baggage or hand/carry-on luggage the company will allow per passenger. There may be limits on the amount that is allowed free of charge, and hard limits on the amount that is allowed.

The limits vary per airline and depend on the class, elite status, type of ticket, flight origin and destination. If a flight is booked together with another flight it may also have different limits (e.g. if another flight on the same ticket is a long-haul flight). The exact baggage conditions are mentioned in the ticket information online.
-- Wikipedia
Legal Definition
The most a bag can weight for each airline carrier. The weight is on the ticket issued. It is 20KG for economy, 30-35 KG business, and 40KG first class. Small hand baggage is limited to 8 KG. The number of bags is also limited.