Amatriel that resists the flow of electrons is called what?

Such a material possesses property referred to as electrical resistance. Resistance is measured in Ohms.  Elements developed with the purpose of causing a specific resistance in electrical circuits are called resistors.

The answer to your question could be "a resistor" but it could also be "an insulator" if they are asking about materials with a complete absence of conductivity (or, infinite resistance). Vaguely worded question.

it's a Resistor <<< not a insulator

Explanation:

1.Insulator is a material in which the electron does not flow freely or the atom of the insulator have tightly bound electrons whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. (so it's not insulator)

:)

2. Resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses (it's resistor)