What is diminishing?

returns:

Diminishing returns is a concept that refers to the decrease in the marginal output or production that occurs when an additional unit of input is added, while all other inputs are held constant. In other words, it suggests that as an organization increases its input (like labor), the output will ultimately rise to a point where every additional unit of input will result in a smaller increase in output. When an organization is experiencing diminishing returns, it should determine when the marginal costs of production outweigh the marginal benefits generated. For instance, an organization may decide to reduce the inputs to maximize the output when it realizes that the extra input is costing more than the value it's creating in return.