Regular soap has two key reactions, one part has molecules that latch on to dirt and grease and shy away from water.
They are insoluble and they come from fat.
The other part of soap loves water and helps to rinse away most of the molecules that have surrounded the dirt, but not all.
This is why soap leaves a film on surfaces.
Detergents are made up of short molecules that, when mixed with alcohol, seek out dirt and grease and surround it.
The difference is that, without the fat of soap, detergents rinse completely away.