What are single (1) character domains?
Single character domains are the rarest domains you can possible register. Most country code domain extensions don’t allow single (1) character domains in the second level. Some countries, like .GY, .GT, .HT, .TT, .AI, .NF, and a few others do allow these registrations.
Single (1) character country code domains are the shortest domains available, they often are formatted like this: L.LL
National Public Radio uses N.PR
MetalPal uses M.TL
BMW uses B.MW
Visa uses V.ME
Human Ventures uses H.VC
BTC Media uses B.TC
Twitter uses T.CO
They are becoming more and more popular for branding and marketing purposes, and are often used as URL shorteners for social media, or as custom branded landing pages. They are often used as short e-mail services and are popular with startups looking to differentiate themselves and secure their branding. One example is the smart personal assistant startup, X.AI
Because they are so rare to register and so short & easy to remember, they are valuable and always in high demand.