A long-period comet is a comet (Sun-orbiting object with a coma and possibly a tail) with an orbital period of 200 years or more. The longest show near-parabolic orbits, i.e., traveling at close to escape velocity, have periods determined to be many thousands of years, and orbits that are often modified during each pass through the inner solar system due to gravitational interactions with the planets. Also, unlike most solar system bodies, their orbits are often far from the ecliptic plane.
Short-period comets are those with orbital periods less than 200 years, which include Encke-type comets with orbits not exceeding Jupiter's, Jupiter-family comets (JFCs) with periods under 20 years along with a low orbital inclination (less than 30° from the ecliptic), and Halley-type comets (HTCs) with periods of 20-200 years such as Comet Halley with its 76-year period. Sun-grazing comets, comets that come within tens of thousands of kilometers of the Sun's photosphere include both long-period comets and short-period comets.
The Oort Cloud is the name given to the collection of long-period comets at the distant region where they reside for most of their existence.