ACP= automatic colt pistol. Colt was the original manufacturer of Browning's design.
.45 auto=.45ACP
To answer one of your original questions, no, there are no other cartridges that
your 1911 will fire. There have been and continue to be made, 1911 style pistols that are chambered for other cartridges. 9mm, 38 super and 10mm come to mind.
The most popular loads are 230 or 185 grain FMJ (full metal jacket) or "ball" ammo and 200 grain SWC (semi wad-cutter) The SWC are great for target use as they leave a nice clean hole in the paper. They typically use a non-jacketed lead bullet which require somewhat more cleaning of the barrel.
Your Springfield is an excellent example of the 1911 platform. Most of them are very good shooters and the company has a very good reputation for customer service.
Welcome to the world of 1911s. They can be quite an addiction
You probably won't stop at just one. They are widely modified for competition and carry use. I carry a 4" Kimber "pro" model daily but also have 5" models for target and steel plate shooting.
Be a little wary of the 1911 pistols with a barrel length shorter than 4" as they tend to be a little less reliable due to Browning's design. That's not to say that there aren't any reliable 3" 1911s.