Why is "do" used here? What does it mean? Can I skip "do"?
Here "do" is used to emphasize "know". Verbs are often preceded by "do", "does", and "did" to emphasize a particular verb, in this case 'know'. When you want to emphasize the main verb in conversation, pronounce "do" with emphasis. Ex： A: Do you like my new shirt? B: I do like your new shirt! Ex：So, you do want to talk about it?