Meaning of $^sB$, s an element, B a subgroup

Question

Let $G = SL_2(\mathbb{F}_q)$, $B$ the subgroup of all upper triangular matrices, $s = \begin{bmatrix} 0 & -1 \\ 1 & 0 \end{bmatrix}$.

What does $^sB$ mean?

I read it from page 4 of C. Bonnafé, Representations of $SL_2(\mathbb{F}_q)$, but there's no definition.

There's also a statement saying $B \cap {}^sB = T$, which is the subgroup of all diagonal matrices.

Answer 1

$^sB=sBs^{-1}$ is defined at the beginning of the book (page xxi "General notation"). It seems that that notation for a group action is more common in Cohomology.