In particular, it has an eye towards modular (i.e. mod $p$) representations of $p$-adic groups. So, it discusses some of the classical theory of representations of $p$-adic groups from a categorical perspective which serves one better in the modular representation setting. It also discusses the fascinating theorem of Kazhdan relating Hecke algebras for $G(F)$ and $G(F')$ where $F$ and $F'$are soemthing like the tilts of $F$ and $F'$.