What is the difference between assimilation, and acculturation?

[?? GIR MISSES CUPCAKE ??]

I am doing a project on the mixed salad and melting pot theories, and i know that M.P is assimilation, and M.S. is acculturation, but i dont really know how to put them in words and describe what each means. One sentence per word is fine!
THANKS A BUNCH!!!!!!!!!