Airlines generally set their baggage allowances by weight and by piece. Here are the differences:

• By weight

The baggage allowance is determined based on the total weight, not the amount of baggage. 

If you see 20 kg besides each passenger’s name in the Baggage page, that means the passenger can check in as many baggage free of charge, as long as they weigh 20 kg or less.

• By piece

The baggage allowance is determined based on the amount of baggage, but each baggage has its maximum weight allowance. 

If you see 1 x 23 besides each passenger’s name in the Baggage page, that means the passenger can check in only 1 baggage with a  weight of 23 kg or less free of charge.