How does 3401(a) and 3121(a) relate to tax forms in the irc?

Question

“wages as defined in section 3401(a)” consist exclusively of remuneration paid to and “defined in section 3121(a)” are exclusively paid by the United States or a company which is resident within territory under the exclusive jurisdiction of the United States, for the performance of "service" as defined by the Classification Act of 1923 mean to any related tax forms?

http://www.youtube.com/watch?v=xuxc2rl38...

Answer 1

3121 defines what wages include and what is subject to employment taxes for different situations.
3401 defines wages for what is subject to withholding taxes by an employer