Final answer:
Differences between House and Senate bills are reconciled by conference committees, which create a unified bill to be sent to the President.
Step-by-step explanation:
Differences in House and Senate bills are resolved by conference committees. When the House of Representatives and the Senate pass varying versions of a bill, they establish a conference committee to reconcile the differences. This committee consists of members from both chambers and works to create a single unified bill that can be sent to the President for ratification. If the president vetoes the refined bill, it requires a two-thirds majority in both chambers to override the veto and enact the bill into law without presidential approval.