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Games in Extensive and Strategic Forms

Sergiu Hart

**Abstract**

This chapter serves as an introduction
to some of the basic concepts that are used (mainly) in
Part I ("Non-Cooperative") of this
*Handbook*.
It contains, first, formal definitions as well as a few
illustrative examples, for the following
notions: games in extensive form (Section 1), games in
strategic form (Section 3), pure and
mixed strategies (Sections 2 and 4, respectively), and
equilibrium points (Section 5). Second,
two classes of games that are of interest are
presented: games of perfect information,
which always possess equilibria in pure strategies
(Section 6), and games with perfect
recall, where mixed strategies may be replaced by
behavior strategies (Section 7).
There is no attempt to cover the topics
comprehensively. On the contrary, the purpose of this
chapter is only to introduce the above
basic concepts and results in as simple a form as
possible. In particular, we deal
throughout only with *finite* games. The reader is referred to the
other chapters in this Handbook for
applications, extensions, variations, and so on.