What is the difference between majoring in Nursing and taking Pre-Nursing in college?

I am looking at colleges and I want to get my BSN. What is the difference between going to a college where I can major in nursing or going to a college where I can take pre-nursing, and then major in something else (like probably some sort of science)
Because some college provide nursing as a major or they have pre-nursing and you choose a different major, like a science.
I don't understand the difference. I just want my BSN.

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