There are several different ways of following a vegetarian lifestyle. Vegetarians do not eat meat and related products. There are all sorts of degrees upto where you can go, from not eating meat for one day a week to never eating meat at all. Go the way you feel your body is reacting best. This can be a way to go from eating meat to becoming a vegetarian, by starting to stay away from meat some of the time.
Vegans are people who follow a lifestyle that refrains from using any animal product.
They do not use milk, eggs or other dairy products. This way of life, however, is a personal choice.