Proofing, or proving, commonly means the final rise of yeast dough after shaping and before baking. The yeast produces gas while the dough expands and develops the structure needed for the oven. Readiness depends on the recipe, dough temperature and strength, not just a fixed time.
The earlier rise before dividing and shaping is bulk fermentation. Some recipes use proofing more broadly for both rises. Separately, proofing yeast can mean checking yeast activity in liquid before mixing a dough; follow the yeast manufacturer's directions.
Reference: Further reading.