A wellbore is any hole drilled for the purpose of exploration or extraction of natural resources such as water, gas or oil where a well may be produced and a resource is extracted for a protracted period.
It is often used interchangeably with drill hole or borehole though typically a "borehole" is referred to in ore mining, exploratory drilling, or pilot holes for installing piers or underground utilities, or any other of a number of single use hole drilling.
See Drilling rig (petroleum) for a diagram of a drilling rig.