admin: prefix before the servername while connecting to DB Engine Query in MS SQL Server

I am using SSMS to connect to DB Engine Query for DAC. I've seen some video tutorials where people use 'admin:' prefix before server name while connecting When trying to connect with that prefix I get an error shown in the picture above. I've checked that SQL Server Browser is running. Also I am running SSMS as an administrator and while Named Pipes protocol is disabled I've changed options to accept TCP/IP as a default protocol. What is the use of that prefix and how to avoid this error? Thanks for your time!