Introduction
A voting classifier combines models with a fixed rule: majority vote or average. But maybe one model is very good for certain kinds of examples and another for others. Maybe one is always slightly too optimistic. A fixed vote can't learn any of that.
Stacking (short for stacked generalisation) asks: why not train a model to learn how to combine them?
Picture a manager with a team of advisors — an economist, an engineer and a lawyer. Over time, the manager learns whose advice to trust for which kind of question. The advisors are the base models; the manager is the blender (also called the meta-learner).