# Why cirq needs Qid class instead of just Qudit class?

I am just wondering in what way cirq.Qid class generalizes qudits. From cirq.Qid documentation we read that it

Identifies a quantum object such as a qubit, qudit, resonator, etc.

I am not sure what this resonator means and if it is somehow connected to other qudits in the system.

Could anyone clarify it?

At some point Qid gained a dimension method that returns an integer telling you how many quantum levels there are... so it really basically is a qudit now.