Veganism is a lifestyle where people choose not to eat animal products and also not to use any other form of animal products.
That would be too extreme for me, but I do not eat meat.
There are many different types of veganism. 
Yeah I guess it just depends on a person's individual beliefs and perferences.
Some vegans are against ANY use of animals for anything, like clothing. They call this an 'ethical vegan'.
That would be very difficult and stressful to try and figure out what everything is made out of.
Vegan diets can reduce the chance of different diseases, like heart disease.
That would make sense.
Some organizations, like the German Society for Nutrition, recommend against vegan diets for kids, and also during pregnancy.