Concepts

Somatic gene therapy is carried to patients cells that are not germline cells, so the modifications are not inherited to to offspring.

Stem cell gene therapy belongs to the somatic gene therapy, but the stem cells can differentiate to various cell types and even to tissues. The effects are then multiplied to new tissues and organs.

Embryonic gene therapy  transduces or transfects an embryo, derived from a fertilized egg, when it contains only a very limited number of cells. By using this technique, transgenic or knockout animals can be created for various disease models. The modifications are inherited to the offspring. Because of ethical issued, this technique is currently not used in humans. 

Germline gene therapy modifies the patients eggs or sperm producing cells. The modifications are not visible in patient, but in the offspring. Due to ethical and technical problems, this method is not used in humans for treating inherited diseases.