Could some one help me with understanding the notion of restriction of scalars? For instance in the case of algebraic group, for instance, $GL_N$, what does restriction of scalars from $K$ to $\mathbb{Q}$ mean, where $K/\mathbb{Q}$ is a finite field extension over the rational numbers?
How to embed $GL_n(K)$ inside $GL_N(\mathbb{Q})$ where $N= [K:Q] \times n$ concretely?
Thank you