Lightning can come from the ground or the sky. It can be discharged from one cloud to another, from a cloud to the surface, from the ground to the sky or from within a thundercloud. Lightning that originates from the surface is often forked, with the tips pointing in an upward direction.
Lightning is a natural discharge of electricity due to the accumulation of oppositely-charged particles in the atmosphere or on the surface. When the buildup of charges is high enough, electricity is discharged in the form of lightning, which is often followed by a bright flash.
Cloud-to-ground lightning strikes occur when electrons travel downward due to the attractive force exerted by the protons on the ground. When the electrons interact with the protons, a channel is formed where electricity is discharged to the surface. Ground-to-sky strikes are infrequent and usually occur from tall structures.