tanh function

The tanh function, also known as the hyperbolic tangent function, is an activation function in artificial neural networks whose output values are constrained between the values of −1 and 1. The following screenshot provides a graph of function f(x)=tanh(x), as output from the Geogebra free online calculator.

target function

In machine learning, the target function is a mathematical representation of the relationship between an ML model's input variables and output variables, which best approximates some desired outcome from a machine learning model.