CS_modules and some generations

The aim of module theory is to better characterize the rings. Especially with the help of the injective modules, QF-rings; which hold an important place in the module theory; can be characterized. CS modules are the generalization of the injective modules. This makes us to think whether we can characterize the rings with the help of the CS-modules. This question got an answer in the literature in the last 10 years. Later on, the CS-modules are generalized as C-modules and weak CS-modules. Finally Tercan defined the CLS-modules and investigated the relation of CLS-modules with the the other modules. Shortly, the CLS-modules got its place in the literature as the latest generalization os CS-modules. In the first part of the thesis, the necessary definitions and theries are explained for clarifying the topic. In the second part of the thesis, the properties of the CS-modules are explained. In the last part of the thesis, the CLS-modules and its properties are investigated.