Let $G$ be a finite $p$-group. Let $(\Gamma_i)$ be a certain descending series with elementary abelian quotients. Let $A=\operatorname{gr}(\mathbb{F}_pG)$ be the graded algebra associated to the radical filtration of $\mathbb{F}_p(G)$, that is, $A$ is the graded algebra with $i$th piece $A_i = J^i/J^{i+1}$ where $J=\operatorname{rad}\mathbb{F}_p(G)$, and whose multiplication is inherited from $\mathbb{F}_p(G)$. Then $A$ is isomorphic to the restricted enveloping algebra of the $p$-restricted Lie algebra associated to the series $\Gamma_i$.
This fact is due to Quillen; it is a high-tech way of expressing Jennings' theorem. Details can be found in Benson's Representations and Cohomology volume 1. It is useful because it gives information on the radical series that would otherwise be hard to obtain, and also gives a good deal of cohomological information about the graded algebra $A$ (e.g. its ordinary cohomology ring is finitely generated over the subring generated by elements of degree at most two). In certain cases (when $\mathbb{F}_p(G)$ is "tightly graded" by its radical filtration) $A \cong \mathbb{F}_pG$ and you obtain cohomological information about $G$ itself.