We use „tud” if we have the „knowledge” usually by learning or practising something, and when we wants to tell that we are „able to do” or „can do” something.
„Én tud(om) a leckét.” – „I know the homework.” (because I have learnt it).
„Én tud(om) a verset.” – „I know the poem.” (because I have memorized it.)
„Én tud(ok) vezetni.” – „I can drive”
„Én tud(ok) táncolni” – „I can dance.”
We use „ismer” if we have the „knowledge” usually by experience, or when we are not talking about the knowledge itself. I mean if you „know” a person is not like if you know your homework. We use „ismer” when we talk about a person we know, . or about things we have experienced (via five sense), like places we have been, or flavours we have tasted.
(Én) ismer(em) a rózsa illatát. – I know the smell of the rose.
(Én) ismer(em) ezt a házat. – I know this house. (like when you go to a house that you haven’t visited for a while.)
Of course there are exceptions. But I think mostly we use these word like this.