The activities distincted because of certain characteristics in the systematically ordered activities according to the Polish Classification of Activities (PKD).

Polish Classification of Activities is contractually agreed, hierarchically structured set of socio-economic activities which are performed by the units (economic entities). According to PKD, activities take place when factors such as equipment, manpower, production technology, information networks or products are linked in order to produce a specific product or service. The activity is characterized by input products (products or services), by the technological process and by output products. The activity may involve a simple process, but it may also involve a whole range of "sub-processes", where each of them is listed in different subclasses, classes, groups, departments, and even classification sections. If the production process is organized as an integrated series of elementary activities, then is treated as one activity.