Budget resolution
A congressional blueprint setting spending and revenue totals. It is not a law and the president does not sign it.
A budget resolution is a concurrent resolution: it is agreed by both chambers but is not presented to the president and does not have the force of law. Its effect is internal to Congress. It sets aggregate spending and revenue targets and allocates them among committees, and those allocations then constrain what individual bills can do without triggering a point of order.
Its other function is procedural. If the resolution contains reconciliation instructions, it directs named committees to produce legislation meeting a fiscal target — and that legislation moves under expedited rules in the Senate.
Passing one is what unlocks the reconciliation process. In years when Congress does not adopt a budget resolution, reconciliation is unavailable.