Transactional memory (TM) is an interesting paradigm for concurrent programming on shared memory architecture. This includes defining a model of TM, as well as the right answer when the implementation of TM's right, what properties can be sure, what the strengths and limitations of TM, and what the inherent trade-offs involved in designing the TM algorithm. Contents: Introduction / System Shared Memory / Memory transactional: A Primer / Issues Truth TM / Implementing a TM / Further Reading / Opacity / Opacity Proving: Examples A / Opacity vs Atomicity / Further Reading / The Liveness of / TM-TM Key Based / Obstruction-Free TM / Liveness of TM / Further Reading / General Conclusion