Veganism is living according to the belief that animal exploitation should be avoided. This means vegans don't eat meat and other animal products, and may not wear leather or use other services which rely on the exploitation of animals.
I feel that there are so many good reasons to be a vegan and very few valid justifications for not being one. Each person has their own reasons for being vegan that tend to fall into one of three buckets:
I think the health benefits (see [[Vegan diet health benefits]]) are nice, and I have definitely become more empathetic to and aware of animal harm (see [[Animal exploitation and veganism]]) since becoming vegan, but I think the reason I am still a vegan largely comes down to the Sustainability benefits. Eating a plant-based diet is one of the simplest and most impactful things an individual can do to help the environment.
I don't think climate change is an individual problem and almost all action to solve it will need to come from government and large businesses, but being personally invested in it helps because you are reducing the economic incentives for businesses which continue to profit off the environmental harm they cause (by not buying meat, for example) and you become a part of the growing population of people who will vote in line with these values - that's one of the only ways we can make the significant policy changes we need to make.
This chart shows the extent of the impact on agriculture, a large portion of which comes from agriculture of animals, or agriculture to grow food for animals.
Source: https://ourworldindata.org/environmental-impacts-of-food
Yet to write: Getting enough protein on a vegan diet