vericose veins

my mother has vericose veins on her calf and they are pretty weird looking. anyway. i was just curious what the surgery was for fixing those? it says on her slides that you can get surgery to fix them, how would that work? i just can't think of what you would do if you got in there with a knife? and also are they dangerous at all? i am just a little worried, i will ask my mom a guess..