What is the US Senate and what does it do notes included?

i am a 27 year old SCOTTISH hugh functioning but mildly autistic adult and a wrestling fan, I just found out that the former WWE CEO Linda McMahon is running for Senate and i thought "what the hell does that mean?" could someone please explain in a simple non-degrading way which i will understand (you do not have to treat me like i am slow or a child or something)