What is ovo vegetarian ?
It's basically vegetarianism but you can eat eggs and not dairy.
Really?
Yeah, in contrast with lacto vegetarianism which is the opposite.
Why are people ovo vegans ?
They see more morality to eating eggs than they do eating dairy products.
lol. Really funny 
They're also called that because ovo means egg in latin.
Good to know
Ovo vegetarianism
Ovo vegetarianism is a type of vegetarianism which allows for the consumption of eggs but not dairy products, in contrast with lacto vegetarianism. Those who practice ovo vegetarianism are called ovo-vegetarians or "eggetarians". "Ovo" comes from the Latin word for egg.
Motivations.
Ethical motivations for excluding dairy products are based on issues with the industrial practices behind the production of milk. Concerns include the practice of keeping a cow constantly pregnant in order for her to lactate and the slaughter of unwanted male
Ovo-lacto vegetarianism
An ovo-lacto vegetarian or lacto-ovo vegetarian is a vegetarian who consumes some animal products, such as eggs and dairy. Unlike pescatarians, they do not consume fish or other seafood. A typical ovo-lacto vegetarian diet may include fruits, vegetables, grains, nuts, seeds, herbs, roots, fungi, milk, cheese, yogurt, kefir, and eggs.
Etymology.
The terminology stems from the Latin "" meaning "milk" (as in 'lactation'