new to all of this and a lot of questions

Hello Ubuntu support community!

Here's what I want to do:

I want to dual boot windows 10 and Ubuntu. I want it so that when I tu on my PC, I will have the choice to boot into Windows, or Ubuntu. Is this possible? I see a lot of talk on here about something called GRUB, and I get the impression thi is something I will need to be able to do that. Is this correct?

I have a Lenovo laptop PC. Its only about a year old. I think I have already successfully tued off fast boot/UEFI. I have also shrunk about 100gb from my drive for Ubuntu.

At any rate, How do I make this happen? That is, choosing which OS to go into upon startup.