Upvote:3
Your baggage allowance is usually determined by either 'Piece Concept' or 'Weight Concept'.
A 'Weight Concept' means you will be allowed to check-in X kg of weight. It doesn't matter how many bags there are as long as the weight of all of the bags does not exceed X kg. Some airlines will have an upper limit; like not more than 10 bags.
The 'Piece Concept' on the other hand usually refers to the number of bags that are allowed for check-in. This rules usually defines how many bags you can check-in and the weight and dimension limits of each bag as well. Since you mentioned Lufthansa you can refer to the below description for both cases.
Checked baggage – Weight Concept
First Class | Business Class | Economy Class
40 kg (88 lbs) | 30 kg (66 lbs) | 20 kg (44 lbs)
These weight limits apply worldwide except on routes on which the Piece Concept detailed below applies. Maximum baggage item weight 32 kg (70 lbs).
Checked baggage – Piece Concept
Business Class 2 baggage items of 32 kg (70 lbs) each Economy Class 2 baggage items of 23 kg (50 lbs) each
Maximum baggage item weight 32 kg (70 lbs).
Some practical examples can be: Weight Concept:
Piece Concept:
Of course, it is in human nature to maximize the benefit of baggage allowance though. :p