How were lamarck's beliefs different from Darwin's?

Lamarcks theory was accepted during Darwin's life, stated that an orgnisims use or disuse of an organ lead to its refinment. That parents could pass on traits acquired during its life to its offspring.

Darwin stated that changes in offspring were random and could not be modified by the parents actions.

Evolution was still the same, changes accumulating over time, but how those changes came about, through the organisim its self, lamark, or randomly Darwin.