We are working with the following question for an exercise:
We got the definition: A subset $K$ in a metric space $(M,d)$ is called precompact if for every $\epsilon > 0$ there exist finitely many points $x_1, \dots , x_p \in K$ such that $K \subset B_\epsilon(x_1) \cup \dots \cup B_\epsilon(x_p)$.
We then have to show that a subset $K \subset\Bbb R^n$ in the space $\Bbb R^n$ (with Euclidean metric) is precompact if and only if it is bounded.