A Pipe rack is a set of steel framed structures (typically triangularly shaped) that drill pipe

Drill pipe

Drill pipe, is hollow, thick-walled, steel piping that is used on drilling rigs to facilitate the drilling of a wellbore and comes in a variety of sizes, strengths, and weights but are typically 30 to 33 feet in length...

 is stacked on for storage or when being readied for use on a drilling rig

Drilling rig (petroleum)

This article lists the main components of a petroleum onshore drilling rig.Offshore drilling rigs have similar elements, but are configured with a number of different drilling systems to suit drilling in the marine environment....

.
Pipe rack also refers to the wooden pad on the drill floor

Drill floor

The Drill Floor is the heart of any drilling rig and is also known as the pad. This is the area where the drill string begins its trip into the earth. It is traditionally where joints of pipe are assembled, as well as the BHA , drilling bit, and various other tools. This is the primary work...

 where the stand

Stand

Stand may refer to:*Stand, Greater Manchester, a residential area in the Metropolitan Borough of Manchester, England*A partnership in cricket*STAND: A Student Anti-Genocide Coalition...

s of drill pipe are vertically stacked when tripping pipe

Tripping (pipe)

Tripping pipe is the physical act of pulling the drill string out of the wellbore and then running it back in. This is done by physically breaking out or disconnecting every other 2 or 3 joints of drill pipe at a time and racking them vertically in the derrick...

 (pulling pipe out of or running pipe into the wellbore

Wellbore

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 of time....

).
See Drilling rig (petroleum)

Drilling rig (petroleum)

This article lists the main components of a petroleum onshore drilling rig.Offshore drilling rigs have similar elements, but are configured with a number of different drilling systems to suit drilling in the marine environment....

for a diagram of a drilling rig.