The yeas and nays are a legislative legal requirement that means when 20% of the voting party of any branch of government requests it, a written list of which people voted in the affirmative and which voted in the negative for any law or act must be provided. This legal requirement acts to hold representatives responsible to their constituency by offering the clear evidence of how the representative is voting for them.
The yeas and nays are listed in the Constitution of the United States which holds transparency as a freedom of the country and a right of the people. Through the yeas and nays there is legal record of the voting majority and an individual record per person. It can also be used to try to influence the representative to vote in a different way.