Being vegan means changing your ways of consuming in order to fight against animal exploitation.
For some people, being vegan is just stopping eating animal products : meat, milk, eggs...
For others, veganism goes beyond food : we also have to stop consuming any products coming from animals: furr or leather clothes, or cosmetics that are tested on animals. We also have to avoid activities that exploit animals : circuses with animals, riding elephants or camels in some countries, zoos...
There are many different reasons to become vegan. One can be vegan because they are against animal exploitation, or they want to act for the environment (see eco-conscious) because mass farming causes deforestation and requires a lot of water and energy, or simply because they want a healthy diet.
However not everyone can be vegan. Vegan food can be more expensive than animal products, so not everyone can afford it, and some people have medical conditions that prevent them from being able to not consume animal products.
For some vegans, changing your ways of consuming isn’t enough : you also have to be an activist for the animal cause. This activism can be done by protesting and raising awareness on animal abuse.
However, some vegans are not very tolerant about those who still consume animal products, without considering the fact that not everyone can be a vegan, even if they want to (see tolerance). Other vegans, on the contrary, will be more accepting of the fact that other people have different ways of consuming.
Although being vegan is eco-friendly, that way of consuming is far from being perfectly ethical and ecological, as there is no such thing as perfectly ethical consumption under capitalism. For example, the production of almond milk is a threat for the bees.