Buying a leasehold apartment and there's a lot I don't know since it's my first time

I want to buy an apartment in Dubai and rent it out, but it's a leasehold listing and I'm confused right from the start about how that differs from freehold. I also need to look into a mortgage, and the pre-approval process and how rent is paid under the contract are all new to me, so I have no feel for it. Advice from anyone with experience would be appreciated.