A domain name is the readable address you register with a registrar, such as
example.com. On its own it does nothing; you have to point it at a host
with a DNS record before it answers as your site.
A domain and hosting are two separate purchases from two separate places. Owning a domain does not mean it is connected to anything yet, and a Birta site works fine at its own address before you ever add one.
For which record to add and why hosts ask for different ones, see connect a domain you already own.