So you want to make your own .com or .org, and let's say you don't want to make a private one only you can use because that is exhausting (because it is, and adds more complexity). This will be a tutorial on how you get your own TLD, owned, and ran by you. Also, note we use the TLD acronym a lot, and it simply means "Top-Level Domain" and is quite common. The parts of a domain name are subdomain (usually www. or blog.) you also might not see them, the domain name (here is dev), TLD is the .com .org, etc.
The backend means, as defined by ICANN as "The role of the registry operator within the Internet ecosystem is to keep the master database of all domain names registered in each top-level domain"
You can buy one or build your own, but it will be a long process, not to mention very difficult. I would say buy one if you can't put a server in your house or office space.
ICANN only takes applicants every few years, so be sure you are not only prepared but you also have a solid $150K to $300K sitting in your bank, as it isn't cheap. The ability for single letter TLDs are either nill or much more expensive, so keep it to 3 letters or more. Do not choose two letters, unless you can convince a country to allow it. They will also most likely take royalties and a good chunk of control. This means to .js, .cs, .bs, .bf, unless it is already a ccTLD (country code TLD) based on the ISO standard, or a country wants it. Sorry.
This can take years, as TLDs like the newly released .gay TLD started their fight in 2012. Now eight years-ish later it is available. There were only four applicants too, some might take more. You might also not be in this step, as most gTLDs (Generic TLD) do not make it past step two as either it is too expensive or they were just rejected.
The process here can also very much differ between circumstances.
Good job, you did it. You spent hundreds of thousands of dollars and spent several years of your life doing a thing. Good news, people will most likely buy it. I mean people buy things like .moe, .ooo, and many other seemingly stupid ones all the time, so even if it sucks (like .lmnop), someone will buy it because they can.