Live comedy can arrive by different routes. A scene may be invented as it happens, shaped during rehearsal or prepared as a set addressed directly to an audience. All of those routes allow room for timing and response. The difference concerns what is already settled when the performance begins, and how the audience relates to the person or people on stage.
These forms overlap without becoming interchangeable. Improvisation can generate material for a sketch. A stand-up set can include an imagined conversation. A prepared scene can leave room for an unexpected audience response. Those meeting places are part of the subject, but they do not remove the useful distinctions between an unwritten scene, a repeatable sketch and a comic's crafted address.
Improv: the scene takes shape in public
In Wikipedia's account of improvisational theatre, performers create dialogue, action and characters collaboratively without a prepared script. A contribution changes the material available to the ensemble. Someone establishes an imagined place, a partner responds to that place and the next action gives it further meaning. The audience follows both the fiction and the fact that it is being made.
Short-form games and longform sets arrange that process differently. A game can begin with a rule that makes the activity immediately legible. A longform set can let scenes connect through returning characters, patterns or themes. The article on longform formats explains those frameworks more fully. Neither removes the need for an actual scene to communicate a relationship or point of view.
Spontaneity is not the same as lack of craft. The ensemble brings habits of attention, movement and shared vocabulary into the room. What remains open is the specific content of the performance. The audience can recognise a format while having no advance knowledge of the story that will grow inside it.
Sketch: material that can be shaped and returned to
Wikipedia's sketch-comedy article describes comic scenes that may be scripted, developed through improvisation or improvised in performance. A prepared sketch gives its performers material that can be rehearsed and presented again. Its shape can be revised before the audience encounters it. That process lets an author or ensemble decide which details belong and which distractions can be removed.
A sketch often gathers around a comic idea. The scene makes the idea visible, develops its consequences and reaches an ending that fits its shape. The idea may concern a relationship, a repeated behaviour or a familiar situation seen differently. The performance still depends on timing and attention, but its basic course can be known to the cast.
When improvisation supplies the starting material, the later sketch need not preserve everything that happened during the discovery. A surprising choice can be retained while the surrounding scene is shortened or rearranged. The distinction is between the method used to find material and the method used to present it. A prepared sketch can have an improvisational origin and still be a prepared sketch.
Stand-up: a crafted address to the room
The stand-up reference article describes a comic addressing an audience through a crafted set, which can contain stories, observations and live interaction. The audience is usually the direct recipient of the material, rather than an observer of a scene between characters. That direct address shapes the relationship between a joke, its delivery and the response.
A set can include acted passages or shifts into another voice. Those moments do not automatically make the whole performance improvisational theatre. They belong within an address whose overall shape can be prepared. Equally, an exchange with someone in the audience may be spontaneous without making the rest of the set unwritten.
The distinction helps explain why crowd interaction cannot establish a form by itself. An improvised set may begin with a suggestion, and a prepared comic may respond to a comment. What matters is the relationship between that exchange and the material that follows. An audience contribution can be the seed of an ensemble's fiction or a moment inside a comic's existing set.
A meeting place between improv and sketch
The Second City's reference account describes revues made with improvisational techniques and rooted in the Compass Players and Spolin's teaching. Its work offers a well-known meeting point between discovering scenes through improvisation and presenting comedy in an arranged form. The fact that the methods meet does not require every scene in a revue to remain spontaneous.
This distinction also matters when reading the history of improvised theatre. An ensemble's creative process and an evening's public structure can have different descriptions. A history of games and scene invention can therefore include work that later becomes prepared material. The relationship is clearer when preparation is described as a process rather than treated as the opposite of theatrical play.
Physical comedy crosses the boundaries
Physical comedy uses the body to make a comic action readable. The reference definition includes mime, clowning and slapstick. A gesture can establish an imaginary weight, show a character's hesitation or reveal a mismatch between confidence and circumstance. That craft can belong to an improvised scene, a sketch or a stand-up performance.
The body's contribution is not limited to an elaborate stunt. Stillness, a changed posture or an attempt to hide a reaction can carry the comic idea. An audience reads the action alongside speech and timing. Prepared and spontaneous performance can both depend on that relationship, even when the overall forms differ.
For an audience, the useful question is what kind of agreement the performance offers. Is the interest in a scene being discovered, a shaped idea being performed or a comic speaking directly to the room? The guide to watching longform follows the audience's attention within the first of those relationships. Recognising the others gives the comparison a wider frame without ranking the forms or predicting which will make a particular person laugh.