J-Cut

An Editing technique used for scene transitions or within a scene which the audio of the next scene or shot precedes the image change.

An example of this can be found in Scott Pilgrim’s opening scene, where Kim’s dialogue begins over the ending of a mid-shot, and J cuts into her in the kitchen.

L-Cut

A Variant of a split edit film editing technique in which the audio form preceding scene overlaps the picture from the following scene.

An Example would be this scene from Fear and Loathing in Las Vegas, where the echoing voice of the receptionist L cuts over our protagonist.