Hyperboloid of One Sheet
The equation which is given here is the equation of a hyperboloid of one sheet.
x^{2}/a^{2} + y^{2}/b^{2} - z^{2}/c^{2} = 1
Here is a diagram of a common hyperboloid of one sheet.
The variable along with the negative in front of it will provide the axis along which the graph is centered.