There are different ones. Delhi weatherpack is probably one of the originals and most common. OEM-type stuff. Awesome for stuff that you want to be able to unplug. They sell single connectors and multiple connectors (2, 3, 4, 6, 12, etc.).
"Deutsch" connector
In some applications soldering isn't the ideal way to go. I solder and use butt connectors (not the cheap ones) from time to time. The butt connectors I use are way thicker and solder well. Others use a rubber cover that has a waterproof seal when you put heat to them and shrink them. Basically needing the right parts and tools to do the job right. Not them cheap-ass auto part store butt-connectors.