The employment structure of a country shows how the labour force is divided between the primary, secondary and tertiary sectors. Different countries have different employment structures. The employment structure of a given country can tell you quite a lot about its economy.
In the richest countries, for example, there will usually be more people working in the tertiary/quaternary sector than in the primary and secondary sectors. In the poorest countries, there tend to be more people working in the primary sector than in either the secondary or tertiary sectors.
Look at the diagram below. Based on the employment structure, which countries do you think are the richest and poorest?
In the richest country (USA), most people work in the tertiary sector. In the poorest country (Nepal), most people work in the primary sector. In Brazil, the labour force is more evenly distributed between the three sectors.
Note that the quaternary sector has been included in the tertiary sector.