Potential Gradient
Also called Electric potential gradient
A potential gradient is the rate at which electric potential changes with position. The electric field component in any direction equals the negative of that rate, so the field points from high potential toward low.
Going from field to potential is an integral. Coming back is a derivative, and it is the direction most students never practise.
Printed on the AP Physics C: Electricity and Magnetism sheet. EK 9.2.B.1 states it in words: the value of an electric field component in any direction at a given location is equal to the negative of the spatial rate of change in electric potential at that location.
The CED does not use the phrase. Searching the C: E&M framework for "gradient" returns nothing; the wording it uses is "spatial rate of change in electric potential". The term is standard physics and standard in textbooks, so it is worth knowing, but do not expect a question to name it.
What the minus sign does. It makes the field point downhill in potential. A positive charge released from rest moves toward lower potential, which is the same statement.
Where it pays. Given you differentiate rather than re-integrating a charge distribution, and on an equipotential surface the potential does not change along the surface, so the field has no component along it and must be perpendicular. That perpendicularity is a consequence of this equation, not a separate fact.
Units: volts per metre, identical to newtons per coulomb.