Suppose some maximal torus $T$ of $G$ is $C_G(T)$, then the set of semisimple elements for which $C_G(s)$ is a torus contains a nonempty open set. Such element are called regular semisimple.
I want to know how to prove this claim and want to find some good examples for some common algebraic groups such as $\mathrm{SL}(n,K)$.
