Basics of setting up a business website--questions

I cheerfully admit to woeful ignorance on how webpages, URLs, domain registration, SEO, etc. work. What I want to do is register a domain, build a website, and utilize standard HTML software to build a simple business website (retail services). There are some things I don’t quite understand, though:

  1. Apparently there are multiple companies that will sell you the “right” to a particular domain name. Who gave them this right? Who owns all the unclaimed URLs out there? How secure would my “ownership” of this domain name, granted by one of these unknown entities, be? Is there an overseeing agency of some type, and if so, where did they derive their authority, and what kind of enforcement power do they have?

  2. I presume my webpages, accessed via my registered URL, would have to be “hosted” on a web server–what’s the ballpark cost/month to do this, assuming nothing fancy (maybe 50 pages of text, and submenus for payment methods, etc.)?

  3. Any recommendations for software to design my home page, etc.? I don’t know HTML and don’t particularly want to learn it.

  4. Is there more to SEO than just stuffing in lines of text, saying, for example, if you wanted to sell bananas, “BANANA BANANA BANANA” over and over and over?

  5. Other than paying ransom to Google, Yahoo, etc., how does one get one’s website to come up higher than 127th on people’s web searches?

Any insights would be appreciated.