What is nihilism and why do some people believe it? List some ways that philosophers have proposed to fight against nihilism. Explain to me in a casual tone
Nihilism is a belief that life is ultimately meaningless. Sounds pretty depressing right? Well, there are a number of reasons why one might feel this way. Do you ever feel like you are just going through the motions each day? You wake up, go to work, get off work, sleep, and the cycle continues. You chased after a goal, such as graduating college or getting that next promotion, thinking it would solve all your problems, only to be disappointed after finally getting it. Then you look around the universe that you lives in and find how insignificant your individuality is in the grand schemes of things, you can't help but think to yourself: man, is there any point to life? Does what I do actually matter at all, especially if I'm going to die anyways? 

If you ever feel this way, know that you are not alone. Many, many philosophers throughout human history have pondered upon this very idea. I'll present a select few philosophers and their proposals to fight against nihilism.

One obvious solution, per Danish philosophers Kierkegaard, is religion. He believes that faith should be our purpose in life, following Him and doing good in this life will reap rewards in the afterlife. 

Now, German philosopher Nietzsche does not agree with that at all; in fact his most famous quote was "God is dead and we killed him". He's talking about how with new advances in science comes the death of religion -- each man must now create his own values and become an ubermensch. The idea of ubermensch, however, kind of throws morality out of window — who is to say one’s value is wrong?

Enter Albert Camus and his idea of absurdism. He compares human life to Sisyphus — rolling a giant rock uphill, only for the rock to fall back down after reaching the top — an absurd and meaningless struggle. He suggests that we accept the absurdity of this world and human existence, and instead embrace the present, because “The struggle itself towards the heights is enough to fill a man's heart. One must imagine Sisyphus happy”.

And there you have it, what nihilism is all about, why it happens and a few ways to fight against it. Note that this is a very extensive topic and what I covered here is only the tip of the iceberg, I’d suggest reading up more if you're interested. Hope it helped!