Full stack web development is a service that encompasses all aspects of creating a web application, from the back-end logic that powers the application, to the front-end user interface that the user interacts with. A full stack web developer is typically skilled in a variety of programming languages and technologies, including languages such as HTML, CSS, JavaScript, and Python or Ruby, as well as frameworks and libraries such as React, Angular, and Ruby on Rails.

In terms of back-end development, a full stack web developer will be responsible for designing and implementing the server-side logic of the web application. This may include working with databases (such as MySQL or MongoDB) to store and retrieve data, as well as creating API's for the front-end to consume. They will also be responsible for server-side routing, handling user authentication and authorization, and other back-end logic.

On the front-end side, a full stack web developer will be responsible for creating the user interface of the web application. This may include designing the layout and appearance of the site using HTML and CSS, as well as adding interactivity and functionality using JavaScript and related frameworks and libraries.

In modern web development, the boundary between frontend and backend development is becoming blur, since the same language and tools is used on both sides, such as javascript in the case of NodeJS and React or AngularJS. This is known as 'Fullstack JavaScript Development'.

In summary, Full Stack Web Development service refers to the complete process of developing, designing and maintaining a web application, with a team or developer that is able to handle both front-end and back-end aspects of the web application, using languages and tools that let them move seamlessly between the client and server side of the web application.