Without a specific equation defined, the answer becomes more abstract. In general then the functions y=f(x) takes values from our domain, the x values, and maps that x to a value in the image of the function, the y values. In simple terms, pick an x value, put it into the equation and then you get out a y value. The inverse function does the opposite of the first function, it takes y values and give x values. Specifically, the inverse function maps a y value to the the specific x value that the original function would map to that y value. In symbols, this looks like
y=f(x) --> f^-1(x) = f(y) = x
for some specific x and y.