budget -> just money
** budget set** -> all the possible bundles of commodity which can be purchased with full or below-optimal utilization of the budget
✅ budget constraint -> P1X1+P2X2≤M
budget behaviour -> how consumer acts
As per NCERT:
The inequality P1X1+P2X2≤M is called the consumer’s budget constraint.
The set of bundles available to the consumer is called the budget set. The budget set is thus the collection of all bundles that the consumer can buy with her income at the prevailing market prices.
It is NOT a budget-set. Please read the NCERT line clearly: "This inequality is called the budget constraint".
