A liaison cutter was a multi-mission, warp-capable small cutter craft based in large starship and starbase shuttlebays in the early 23rd century. In some ways, liaison cutters were the forerunners of the Starfleet runabouts used in the 24th century.
A typical starship-based liaison cutter was 10 meters long and consisted of a main cabin (with helm controls and passenger seating), a sensor pod accessed via a hatch and ladder in the main cabin ceiling, and a detachable cargo section connected to the main cabin by a short tube which also served as an airlock. (One cynical observer likened its appearance to "a pregnant whale with a tumor on its head".)
Liaison cutters were rather clumsy craft and not very maneuverable, especially within the confines of a starship shuttlebay, so they were being gradually phased out in favor of smaller, nimbler shuttlecraft by the mid-23rd century. (TOS novel: Best Destiny)