  In two lectures, we overview the renormalon and renormalon-related techniques
and their phenomenological applications. We begin with a single renormalon
chain which is a well defined and systematic way to specify the character of
corrections in inverse powers of the total energy to observables directly in
Minkowski space. Renormalons demonstrate also presence of nonperturbative
contributions. We proceed then to multirenormalon chains and argue that they
are in fact not suppressed compared to a single chain. On one hand, this
phenomenon might be a mechanism for enhancement of power corrections. On the
other hand, the derivation of relations between power corrections to various
observables becomes a formidable task and asks for introduction of models. In
the concluding, third part we consider dynamical models for nonperturbative
effects, both in infrared and ultraviolet regions, inspired by renormalons.
