Why do bills pass the senate and then go back to the house?

If the bill passes by simple majority (218 of 435), the bill moves to the Senate. In the Senate, the bill is assigned to another committee and, if released, debated and voted on. ... Finally, a conference committee made of House and Senate members works out any differences between the House and Senate versions of the bill.

Explanation:

i believe that the answer to the question provided above is that the role of campaign committees is to act as a bridge between state and local campaigns.