Quarinteen

Hello everybody, I am new here. I am 40 I live in Vegas. I just decided to learn guitar and I have been learning about tuning. I was reading there is a “standard “ of A440 hz which the United States implemented in the 50’s or something. I understand what the 440 is but what is the A for? The next part I want to understand is how it works exactly. If I tune my guitar’s E string the proper frequency from what I understand; why c isn’t saying much but still. The big E has a frequency of 329.63hz. So where is this A440 A432 tuning talk my place? Is it something they have done to modify speakers? I am sorry for the ignorance but I am very curious how all this works