Clarifying understanding of Poisson Brackets in Hamiltonian Dynamics

Question

I'm just reading through my textbook and would like to clarify my understanding of 'Canonically related variables'. In my textbook, it says that if $Q_i$, $P_i$ are related to $q_i$, $p_i$ by a canonical transformation then: $$\{Q_j,P_k\} = \delta_{j,k}$$

I'm not exactly sure what $\delta_{j,k}$ refers to, but from what I have gathered - does this refer to the number of degrees of freedom shared by $Q_j$ and $P_k$?

Thanks, just wanted to verify my understanding.

Answer 1

No, it's just the Kronecker delta: $\delta_{i,j}$ equals $1$ if $i=j$ and $0$ otherwise.