Linked from
The 15 pages that link to Canonical ensemble, each with the reason it gives.
Thermodynamic equilibriumRelated: It describes equilibrium under thermal contact with a reservoir.
Boltzmann distributionNarrower topic: The distribution gives state probabilities for this ensemble.
Grand canonical ensembleCompared with: It permits energy exchange but keeps particle number fixed.
Helmholtz free energyRelated: Its partition function determines the Helmholtz free energy directly.
Gibbs paradoxNarrower topic: Its partition function makes the particle-counting correction explicit.