Originally, a military sidearm with enough punch to put down a drugged, crazed opponent (i.e., the Moros in the Phillipines in the early 1900's).
The gun is noted for being single action, having a grip safety and a thumb safety. Originally had single stack magazines holding 7 rounds. This is bumped to 8 in modern times and some magazines are double-stacked (staggered) holding 14 rounds. Caliber is usually .45 ACP.
Today, still a very effective and reliable sidearm for police and special military forces. If you have ever shot one, you will know that 1911's are great guns, although a bit larger and heavier than competitive offerings.