A security solution that detects identity-based threats and suspicious activities in on-premises Active Directory environments
The gMSA has no specific requirement for naming convention, the $ sign is like to tell the system that it's not a normal account (derived by the computer class) and the password is auto-managed by active directory. Even if you specify a password AD will replace with a new strong password, which changes automatically every 3 days.
The password is a concatenation of RootKey+gMSAguid+EpochID=gmsapassword (epochID is a special identifier of a specific time slot in the calendar, starting from year 1601, for which AD makes all little slots of 10 hours each, and each one having an ID), going 5 mins in the future to accomodate kerberos skew time