Modifier Stack
Blender's non-destructive list of operations applied to an object.
Modifiers are procedural operations (mirror, bevel, subdivision, arrays) stacked on an object and evaluated top to bottom. The stack is non-destructive: the underlying mesh stays editable while the modifiers keep doing their work, and the order of the stack changes the outcome. It is basic procedural modeling, with Geometry Nodes as the advanced version.
Related: Subdivision Surface · Modeling
These fundamentals are covered hands-on in Blender Geometry Essentials 01, free with a free account.