For people taking chemotherapy, there are EARLY side effects, which are the direct effects of the agent upon body tissues. These tissues either die, or recover from the effect of the chemotherapy completely, or somewhat.  For instance, early side effects for many chemotherapy agents are known to be nausea and vomiting, diarrhea, hair loss, and so on.  These are symptoms which are temporary and which go away.  The tissues involved might be damaged somewhat, but recover sufficiently to function well.

Other side effects may involve bone marrow destruction, or specific damage to certain organs [like the heart for doxorubicin, or the urinary tract for ifosfamide, or lungs or liver for gemcitabine.] These effects may be permanent.  Sometimes these effects will show immediately, and the agent is stopped.  However, sometimes the damage is not so great, but as time goes on and the normal aging of tissue occurs, the damage becomes more apparent because the organ's reserve is gone.

LATE effects [the euphemism for permanent damage and further risks which may not be apparent at the beginning] can be from tissue damage that is subtle, and take longer to show itself.  The heart failure from doxorubicin's destruction of heart muscle does not show early on.  Pulmonary fibrosis from BCNU is a late effect.  Myelodysplasia [failure of bone marrow to produce enough blood cells] and secondary cancers [often leukemia] from chemotherapy, as well as the cognitive late effects are described in separate sections below.

Additionally, each chemotherapy agent has its own spectrum of possible late effects/permanent damage.  If these are known, they are listed in the package insert for the agent. One should be aware of these, so that if there are related early side effects, they are quickly noticed and the agent stopped.
