The warp fields of the Enterprise and Columbia making contact
A warp field is the means by which a warp drive propels a starship at faster-than-light (or warp) speeds. Generated by field coils, usually found in nacelles, the field surrounds the ship asymmetrically, which causes the space within it to accelerate.
The warp field, also known as a subspace field, is a subspace displacement which warps space around the vessel, allowing it to "ride" on a distortion and travel faster than the speed of light. (ENT: "Cold Front") This has the physical effect of reducing the inertial mass of any object encompassed by the field. (TNG: "Deja Q", DS9: "Emissary")
During emergency situations where the transfer of crew or other objects is necessary while in warp, the warp fields of two vessels may be brought into contact with each other and merge to form one, provided both ships remain motionless relative to each other and at the same warp velocity. (ENT: "Divergence")
The warp field of a Federation starship like the USS Enterprise-D left behind an electromagnetic signature on Data's internal servo fluid system. (TNG: "Schisms")
Warp fields can be disrupted by inverse graviton bursts. In 2375, the IKS Ning'tao, under the command of Dahar Master Kor, managed to destabilize the warp fields of several pursuing Jem'Hadar attack ships by using the technique. (DS9: "Once More Unto the Breach")
In 2063, Geordi La Forge was able to modify the warp field of the Enterprise-E to match the exact chronometric readings of the Borg sphere they had pursued back in time, and was able to recreate the temporal vortex that the sphere had created, and return the Enterprise to the 24th century. (Star Trek: First Contact)