On almost projective modules

This thesis aims to introduce the concept of almost projective module and its various characterizations. The concept of almost projective module, introduced by Roberto Martinez Villa in 1980, has played an important role in solving some problems in the representation theory of artin algebras. The thesis study consists of three parts. In the introduction, the historical development process of the concept of almost projective module is expressed. In the second part, the basic definitions and properties that will be used in the thesis study are given. In the third part, almost projective modules are examined under three subheadings on hereditary, artin and non-hereditary algebras, respectively.