A distributed system is one in which the application and its architecture are distributed over a large number of machines and preferably physical locations. More simply, a distributed system is one where the goal of the system is spread out across multiple sub-systems in different locations. This means that multiple computers in multiple locations must coordinate to achieve the goals of the overall system or application. This is different than monolithic applications, where everything is bundled together.
Let's take the example of a simple web application. A basic web application would run with processing, storage, and everything else running on a single web server. The code tends to run as a monolith—everything bundled together. When a user connects to the web application, it accepts the HTTP request, uses code to process the request, accesses a database, and then returns a result.
The advantage is that this is very easy to define and design. The disadvantage is that such...