The given graph is a representation of kinetics of a reaction
The y and x axes for zero and first order reactions, respectively are
$$\bullet$$ For zero order reaction
r = k[A]0
r = k (constant)
hence, 'y' as 'rate' and 'x' as concentration will give desired graph.
$$\bullet$$ For first order reaction
$${t_{1/2}} = {{0.693} \over k}$$ (constant)
hence, 'y' as 't1/2' and 'x' as concentration will given desired graph.