Okay, imagine you have a really fancy calculator that just does addition. That's basically what the Standard Adding Machine Company used to make a long time ago.
The adding machine was a big box with buttons on it, kind of like a keyboard. When you pressed a button, it would add a specific number to a total.
For example, if you pressed the "1" button five times, it would add 1+1+1+1+1 = 5 to the total. The machine would keep track of this total and show it to you on a little screen.
Before computers were invented, people used adding machines like these to do math quickly and accurately. They were especially helpful for jobs that involved a lot of numbers, like accounting or banking.
So, the Standard Adding Machine Company was a company that made and sold these machines to businesses and individuals who needed them. Nowadays, we have computers that can do all kinds of math for us, but back then, adding machines were a very important tool!