both 工作 上班 mean WORK, sometimes they are exchangeable and sometimes definitely not.
上班 ，上means to go ,班means shift, go to the shift. so 上班 is going to a certain place in a certain time on a regular basis,to work.
and it also means during work. there are plenty of example sentences in the video.
on the other hand, 工作 ，工originally meant a tool, and 作 meant a carpenter is working on a craft . so 工作emphasize that you are really working ,producing values.
工作and 上班are exchangeable when you assume that when you are in the workplace ,you are really working ,not just killing time.
another big difference is the usage, 上班is just a verb ,but 工作can be both a verb or a noun. it also means job.