What means the following expression:
Every action of an affine algebraic group on an affine algebraic variety can be linearized.
What means the following expression:
Every action of an affine algebraic group on an affine algebraic variety can be linearized.
This statement should mean the following:
There exists a finite-dimensional vector space $V$ on which the affine algebraic group $G$ acts in such a way that the affine algebraic variety $X$ is a subvariety of $V$ and the action of $G$ on $V$ restricts to the given action of $G$ on $X$.