Transfer orbits are paths that spacecraft use to move from one orbit to another, typically between two celestial bodies. The most common type is the Hohmann transfer orbit, which allows a spacecraft to efficiently travel from a lower orbit to a higher one, or vice versa, using minimal fuel. This method involves two engine burns: one to leave the initial orbit and another to enter the final orbit. These orbits are crucial for missions to planets like Mars or Jupiter, as they help optimize fuel usage and travel time. By carefully planning the transfer orbit, mission planners can ensure that the spacecraft arrives at its destination at the right time and position.