Heh. This one is short and sweet. I feel like I understand it pretty well.
The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Place of Chusing Senators.
It’s up to the states to decide how to hold elections. However, Congress reserves the right to override this if necessary. In other words, hold on to your butts. This could get entertaining in the near future. Or the power could be used for Good. Hope springs eternal…
Senators were not directly elected when this was written. The 17th Amendment changed this in 1913.
The Congress shall assemble at least once in every Year, and such Meeting shall be on the first Monday in December, unless they shall by law appoint a different Day.
Being a member of Congress was not a full-time job, back in the day. Communications being what they were, they needed to set out a time to assemble and a minimum interval. This comes from the memory of Parliaments in English history being rather infrequently and reluctantly called. They recognized that national government needed to meet on a regular basis.