The definition is Simply, full stack developer is a kind of people who master a variety of skills and use these skills to complete a product independently. A top voted answer on Quora explained that what is a full stack developer: A full stack developer is an engineer who can handle all the work of databases, servers, systems engineering, and clients. Depending on the project, what customers need may be a mobile stack, a Web stack, or a native application stack.

In fact, “full stack” refers to the collection of a series of technologies needed to complete a project. “Stack” refers to a collection of sub-modules. These software sub-modules or components combined together to achieve the established function while without the need for other modules.

the discussion about full stack developer is actually the debate on the depth and breadth of skills. Especially at the OSCON conference, a Facebook engineer said they only hired a “full stack developer.” This topic came as a result of a heated discussion about the strengths and weaknesses of being a full stack developer.

Advantages: The full stack developers involved in a horizontal technical requirement, so that he/she can make a prototype design for a product very rapidly with his wide range of techniques. With the full stackability, they have a broader angle of views and a more active mindset. Moreover, they will be more sensitive to techniques and products. So, this kind of people can always have his/her opinions towards the product or design.

From another aspect, he/she can provide help to everyone in the team and greatly reduce the time and technical costs of team communication, technology docking. So many of them become entrepreneurs or as technical partners in start-up companies.

Disadvantages: It is precisely because of the horizontal technology development, some the full stack developers cannot be expert in one skill. Most of them who claim to be “full stacks developer” are only know a little about the multiple skills. As for how to make the architecture more suitable for the modular development, that’s a question.

A qualified full stack developer should have functional knowledge and capabilities for all aspects involved in building the application. Analisis, Devops or continuos integration(deployment) are things that are need, that sometimes they forgot like on this image. Deployment, security and testing should be part of the knowledge to be a full stack developer. I know that testing is a part of everything like security but alot of people forget about it.

I take this information from this post from hackernoon, if you want to read more on the topic.