A TLD, or top-level domain, is the last part of a domain name: .com,
.dev, .app, and hundreds of others. It is managed by
ICANN and a designated registry per extension, but
it plays no part in whether DNS actually resolves correctly. A .dev domain
and a .com domain connect the same way once you own one.
Which TLD you pick is a branding decision, not a technical one, and Birta does not care which extension your domain carries.
For how to actually connect whichever domain you already own, see connect a domain you already own.