The buoyant force is an upward force exerted on a body that is submerged in a fluid. Briefly, the Archimedes principle states that this force, the buoyant force of a body submerged (fully or partially) in a fluid, is equal to the weight of the displaced fluid.
As an illustration, consider a 500ml container, that is filled with water. In this container, you placed a toy that's 10 grams in weight. When you placed the toy in the container, 6 ml of water was displaced (this could mean that 6ml was thrown out of the container, or if the container has graduations, the reading went up by 6ml). The displaced liquid here is the 6ml of water. Assuming water has density 1g/ml, the weight of displaced fluid is 6 grams. According to Archimedes Principle, the buoyant force, then, is equivalent to 6 grams (`6g*(1kg)/(1000g)*(9.8m)/(s^2)=0.0588N` ` `). This means that while there's 0.98 Newton(`10g*(1kg)/(1000g)*(9.8m)/(s^2)` ) of force downward due to the objects weight, there's a 0.0588 Newton force (buoyant) upward. The result is that the apparent weight of the object submerged in the liquid is only 0.98 - 0.0.0588 = 0.0392 N downward force. Notice that this is lower than the actual weight of the object. The buoyant force is responsible for feeling lighter when you're taking a swim.