Basic Understanding about Babylon JS Technical Terms

Hi all,
I wish to understand some technical terms of babylon js what exactly it does. Please help me on this.
While doing the scene optimization, ActiveMeshesEvaluation is a term I heard. What is this exactly, and an event(observable) is also available in scene regarding this. What it exactly will do.

As far as I understand it during active meshes evaluation the world matrix for each active mesh is computed. The observables allow you to execute code just before or just after this happens.

This may be of interest
How to optimize a scene with 10k mesh instances? - #4 by Evgeni_Popov as it mentions scene._evaluateActiveMeshes()


Thanks for your reply @JohnK . What is the use of defaultrenderpipeline() . It is offering some features as default. If I need to add other some post processing properties to it which is not available in the default properties of defaultrender pipeline. Is it possible?