Nuclear reactions play an essential role to address the many-body problem of nuclear structure. Reactions are used to produce exotic nuclei, to populate specific nuclear states and the so-called direct reactions have been a unique tool to built up our representation of the nuclear shell structure. In this lecture, the basics of radioactive beam production are described and direct reactions are introduced. In particular, spectroscopic factors (SF) are defined and discussed. Transfer and knockout reactions are introduced in the light of today’s experiments and detection setups.