Combinatorial group theory is a loosely defined subject, with close
connections to topology and logic. With surprising frequency, problems
in a wide variety of disciplines, including differential equations,
automorphic functions and geometry, have been distilled into explicit
questions about groups, typically of the following kind: Are the groups
in a given class finite (e.g., the Burnside problem)? Finitely
generated? Finitely presented? What are the conjugates of a given
element in a given group? What are the subgroups of that group? Is there
an algorithm for deciding for every pair of groups in a given class
whether they are isomorphic or not? The objective of combinatorial group
theory is the systematic development of algebraic techniques to settle
such questions. In view of the scope of the subject and the
extraordinary variety of groups involved, it is not surprising that no
really general theory exists. These notes, bridging the very beginning
of the theory to new results and developments, are devoted to a number
of topics in combinatorial group theory and serve as an introduction to
the subject on the graduate level.