What is the difference between 探望 and 看?
「探望」has a tendency to describe visits which "aims to make somebody happy or feel better", like visiting a relative/close friend whom you haven't visited for quite a while (not required), or visiting somebody in a bad situation (e.g. injured/ill). In this case, both「探望」and「看」can be used.

In most other cases, using「看」may be more appropriate, for example: to visit a doctor (due to sickness) (as mentioned by @user58955) (note, it can be correct to say「探望醫生」when you are visiting a doctor to thank one for healing you, for example), to visit an exhibition. There might be exceptions but I can't think of any now.