迟到 ＝ not punctual; not on time. 晚 = evening; after an appointed time.

Both means late but, "late" in different definitions. "It's getting late" = in this case you use 晚 but, "I'm going to be late for school" = in this case you use 迟到. Hope it helps :D

迟到 means be late for example It is the norm for Bob to be late.迟到对鲍勃来说是家常便 晚 only means late for example It is too late,so i have to go to bed.现在太晚了，我不得不去睡了