Lacto-Ovo Vegetarian: Now we're getting somewhere. These eat no meat at all. They will consume eggs and dairy products to a certain extent, some more than others. This is probably the largest class of vegetarians. I still don't know what the difference between Lacto-ovo vegetarian and just plain vegetarian is.
Vegetarian: Does not eat meat. Pretty much the same as Lacto-Ovo vegetarian if you ask me.
Ovo Vegetarian: I'm sure these are out there, vegetarians that will eat eggs but not drink milk or use other dairy products. You don't see this too much.
Lacto Vegetarian: Similar to Ovo Vegetarians except they will use dairy but not eggs. Maybe a finely split hair? Possibly but there is a name for everyone.
Vegan: These people use no animal products whatsoever or only under absolute duress (such as they say there is animal products in cars and computers, some things just can't be helped.)