u/InjuredUser69

I developed a small drip under the sink and confused about what the original plumber did and the lack of beveled seals or seals on the pipes. Are there fitting under the sink that don’t need gaskets? Slip fittings.
The dark piece had no gaskets, as well as the elbow at the 90 degree slip fittings pipe going into the dark pipe that adapts to the trap. Is this right?