My first week at my workplace as a fresher was filled with a lot of events including orientations, fun activities and training sessions where they talked about what is expected of me as an employee and what are the benefits other than my salary that I will be receiving from my organization . Most of the Multinational Corporations will keep the buffer of first week of joining to have you go through all the formalities and document verification. They will give some entry level training where you will be introduced to the workflow , company hierarchy and the general working environment.
The experience of a fresher can be different from that of an experienced employee, I cannot say much about the latter.
But Mostly, you will be spending your time going through presentations, trainings, meeting new people and understanding who's who in that organization.