What is your take on extraterrestrial intelligences, have you seen "UFO"s , or even been in one if you lucky and caught by a surprise ? Have you met any people from other planets ? Or simply if you have not, what are your thoughts about the topic, and would you like to have an experience ?
Do you believe in the existence extraterrestrials ? (Belief is based on faith or trust without looking at the evidence, data, mathematical models, that is because your friend saw something, and you trust your friend, without research, that is belief)
Do you understand the existence of extraterrestrials ?
(Understanding is based on collecting data , evidence, mathematical models such as drake equation, astrobiology research etc and deriving a conclusion)
Do you know the existence of extraterrestrials ?
(That is when you have had your own personal experience, scrutinized it to be legitimate experience, as well as comparing your experience with other's evidence data and so on)