Set to true to begin logging messages to the Unity Console to see a read-out of what PoolManager is doing while your game runs.
This is available in Unity's Inspector (and is an easier way to use this feature. Just set the check-box and start the game.) Doing this through code has the advantage that you can turn it off and on when you need it though.
You can also turn logMessages on at the PrefabPool level via the Inspector, or if creating PrefabPools via code. This means you can see messages related to only a specific prefab, rather than the whole pool. Turning on SpawnPool.LogMessages will turn this feature on for all PrefabPools, but turning it off will just allow the PrefabPool setting to determine if it will log messages or not.