People who have work or who are in work have a job, usually one which they are paid to do.
工作Fewer and fewer people are in work. 越来越少的人有工作。
When you work, you do the things that you are paid or required to do in your job.
工作I can't talk to you right now – I'm working. 我这会儿不能和你说话–我正在工作。
I work in NO School. 我在NO学校工作。
work 和 job 都翻译为“工作”,job 为可数名词,一般与“职业、职位”有关,或表示某人的“份内事”; work 作“工作”讲时是不可数名词,常指具体的“劳动、作业”或“(待做的)工作或事务”等,也可能表示“上班”。