This refers to mass deployment of the work at the end users' locations. Successful deployment at pilot sites does not automatically mean that the general deployment will be successful. In fact, during experimentation, users have a motivation that the end users lack. Additionally, each malfunction of the work is recorded during experimentation. deployment generally implies changes in the way the users work, which is an obstacle for acceptance of the product by the users. In fact, end users generally look for a psychological motivation in their professional lives (increase in revenue and hierarchical position) and job security. A change in their work habits is an obstacle to these objectives.
Thus, "change management" is used to refer to all elements that allow you to ensure that the end users will really use the product, and therefore change their habits. This term encompasses, among other things, the training of users in the use of the product, as well as user support (hotline).
On the other hand, if the project is intended for a large number of end users, it is not always feasible to go directly from experimentation to general deployment. Depending on the work, it may be necessary to do tests on increases in output, i.e., simulate a gradually increasing number of users in order to estimate whether the product is potentially able to tolerate the total output (simultaneous use by the number of users provided for in the specifications).