Nirvana and Moksha are similar in that they are both ultimate goals in practicing the religions. Nirvana is the process of achieving total inner peace in oneself, and it is the ultimate goal of Buddhism. Moksha, likewise, is the release from samsara (cycle of death and rebirth) which helps Hindus find total peace in themselves (nirvana), which is the ultimate goal of Hinduism. So, the two are both ultimate goals (one being the ultimate goal of Buddhism and one being the ultimate goal of Hinduism), and they both are centered around this idea of finding total peace in oneself.
Hope this helps! I learned about the Eastern Civilzations last year so the concepts are still pretty fresh in my mind. :)
