Editors use J and L cuts to allow audiences to see the context of the dialogue rather than just the dialogue itself.

What makes a L-cut or J-cut work is the combination of dialogue and imagery. For an L-cut, the dialogue continues as the camera cuts to another image. For a J-cut, the dialogue plays while we see contextual images, but then cuts to the source of the dialogue.

Using a J-cut or an L-cut is all about keeping the flow of the edit moving without becoming boring. If a J-cut or L-cut is performed properly, then the audience will never notice it taking place. This same theory is really true for any editing technique.

Image: an example of an L-cut 

Think about the films we watch and the dialogue sequences within them. During these sequences, the editor isn’t constantly cutting back and forth to each character as they talk. Doing this would be very distracting. Instead, an L-cut is used.

This technique sees Character A speaking, but then the scene cuts to Character B as Character A continues their dialogue. By doing this, the editor is allowing viewers to hear the dialogue while also seeing the reaction of Character B, giving the audience a better overall understanding of the scene.

Image: an example of a J-cut 

The J-cut is the opposite of the L-cut. With this technique, the viewer hears the dialogue of Character A — but only sees Character B on screen. From this shot of Character B (which provides emotional information and context for the scene), the editor cuts back to Character A. 

(Information from: https://www.premiumbeat.com/blog/what-is-j-cut-and-l-cut-in-video-editing/)

J-CUT – A J cut is a variant of a split edit film editing technique in which the audio from a following scene overlaps the picture from the preceding scene, so that the audio portion of the later scene starts playing before its picture as a lead-in to the visual cut. 

https://en.wikipedia.org/wiki/J_cut#:~:text=A%20J%20cut%20is%20a,audio%20lead%20or%20audio%20advance.

L-CUT – An L cut is a variant of a split edit film editing technique in which the audio from preceding scene overlaps the picture from the following scene, so that the audio cuts after the picture, and continues playing over the beginning of the next scene.

https://en.wikipedia.org/wiki/L_cut#:~:text=An%20L%20cut%20is%20a,beginning%20of%20the%20next%20scene.

J cut: A J cut is a variant of a split edit film editing technique in which the audio from a following scene overlaps the picture from the preceding scene, so that the audio portion of the later scene starts playing before its picture as a lead-in to the visual cut. Also called an audio lead or audio advance.-Wikipedia

L cut: An L cut is a variant of a split edit film editing technique in which the audio from preceding scene overlaps the picture from the following scene, so that the audio cuts after the picture, and continues playing over the beginning of the next scene.-Wikipedia

Both cuts combine dialogue and imagery.

J-cut: Dialogue plays while we see contextual images, but then cuts to the source of the dialogue.

L-cut: Dialogue continues as the camera cuts to another image.

A J cut is a variant of a split edit film editing technique in which the audio from a following scene overlaps the picture from the preceding scene, so that the audio portion of the later scene starts playing before its picture as a lead-in to the visual cut.

An L cut is a variant of a split edit film editing technique in which the audio from preceding scene overlaps the picture from the following scene, so that the audio cuts after the picture, and continues playing over the beginning of the next scene.

A J cut is where the audio from a following scene overlaps the picture from the preceding scene, so that the audio portion of the later scene starts playing before its picture as a lead-in to the visual cut.

An L cut is where the audio from preceding scene overlaps the picture from the following scene, so that the audio cuts after the picture, and continues playing over the beginning of the next scene.

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A J cut is when the audio from the next scene is played into the ending of the last scene before the cut into the new scene.

An L cut is when the audio from the previous scene is played into the next scene.

J Cut – a film editing technique in which the audio from the next scene overlaps the picture from the current scene

L Cut – a film editing technique in which the audio from the current scene overlaps the picture from the next scene