Is a martini a cosmo?

Excuse me, I've been wondering about something for a while and I'm hoping you can help me clear it up. I've heard people talk about martinis and cosmos, and I'm just not sure if they're the same thing or not. Could you please explain the difference between a martini and a cosmo? I'm quite interested in learning more about the intricacies of mixed drinks and how each one differs from the others. Is a martini simply a variation of a cosmo, or are they two completely different cocktails with distinct flavors and ingredients? Your expertise in this field would be greatly appreciated.