Question: From parametric to surface eq.

Hello my Maple friends! :)
I was wondering if there is any command in Maple that can help me find the equation of a surface from it´s parametric form and the other way around, a parametric form from a surface equation!
For example, if
x :=(s, t) -> s cos(t)
y :=(s, t) -> s sin(t)
z :=(s, t) -> s^2

then S: x^2+y^2=z

Thank you for your help.
English is not my mother tongue; please excuse any errors on my part.

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