The upward buoyant force on a body immersed in fluid is equal to the weight of the fluid displaced by the body. This is known as Archimedes' Principle.

Here's a more detailed explanation:

* Buoyancy: Buoyancy is the upward force exerted by a fluid that opposes the weight of an immersed object.

* Displacement: When an object is immersed in a fluid, it pushes aside (displaces) a volume of that fluid.

* Archimedes' Principle: This principle states that the buoyant force on an object is equal to the weight of the fluid that the object displaces.

Example: Imagine a boat floating on water. The boat displaces a certain volume of water, and the weight of that water is equal to the upward buoyant force acting on the boat, keeping it afloat.