How does Digital Ocean work?

I’m sorry in advance if this is the wrong location for this question, but I’m curious as to how Digital Ocean actually works, and what it provides. I’ve held off on purchasing a droplet until I can decide whether or not it will fit my needs. Currently I have a domain with Dreamhost, and I’m looking to perhaps find a more reliable service, but as I understand it currently, with Digital Ocean, I’ll receive a cloud-based server, and I’ll still need to purchase the domain separately through Dreamhost or another provider?

Also, when I’ve purchased a droplet, what does that give me? Is it the virtual hardware for a server in which I’ll need to set up a server OS, or is it ready to host immediately? Am I able to use a server OS in lieu of any theoretical ready-to-use server software pre-configured?

Lastly, is there a more effective solution that Dreamhost for a simple project site? I’m a student at present, and just using the site to learn more on my own time about HTML, CSS, and Javascript (I won’t be using Wordpress or anything similar, more than likely). I doubt there will be much database work involved.