Cement paste
The mixture of cement and water that coats and binds the aggregate. Paste is where strength, shrinkage, permeability, and most durability problems originate.
What does cement paste mean?
Aggregate is generally stronger and more stable than the paste around it, so concrete's weaknesses are usually paste weaknesses. More paste means easier finishing and more shrinkage; less paste means a harsher mix that resists cracking better. Understanding that a slab's surface is mostly paste explains why finishing and curing decisions dominate surface durability.
In practice
When a finisher works a surface too much, they are pulling paste and water to the top and building the weakest possible layer exactly where the traffic goes.