What is a Server?
The server is a computer that receives incoming requests from the client. These high-powered computers provide shared resources that networks need to run, including file storage, security and encryption, databases, email, and web services. Though there are machines made and optimized for this particular purpose, any computer that is connected to a network can act as a server. In fact, you will often use your very own computer as a server when developing apps. The data that the server sends back can come in different forms. For example, a server might serve up an HTML file, send data as JSON, or it might send back only an HTTP status code. Server-side languages used by developers are Ruby, PHP, Python, Java, and .Net.
What is a Database?
Databases are the brains that make websites dynamic. They are commonly used on the back-end of web applications. These databases provide an interface to save data in a persistent way to memory. Storing the data in a database both reduces the load on the main memory of the server CPU and allows the data to be retrieved if the server crashes or loses power. Whenever you request something on the website, it is database responsibility to accept that query, get the data, and return the response to the website or application. The client can change the information in a database from the browser and the database can accept this new and edited data. Many requests sent to the server might require a database query. A client might request information that is stored in the database, or a client might submit data with their request to be added to the database.
What is Middleware?
Middleware describes any software on the server that makes the connection between an application or web front-end and its back-end. Middleware is any code that executes between the server receiving a request and sending a response. These middleware functions might modify the request object, query the database, or otherwise process the incoming request. Middleware functions typically end by passing control to the next middleware function, rather than by sending a response. It is like a plumping in the site and it pipes any communication, like requests and responses, back and forth between your application and your server/database. Middleware (server-side software) facilitates client-server connectivity, forming a middle layer between the app(s) and the network: the server, the database, the operating system, and more. Middleware can be multi-layered, organized into different layers of a site, whether it’s the presentation layer or the business layer. This is also where Web APIs can play into the stack, providing a bridge between the business layer and presentation layer. Good middleware can also maximize IT efficiency and power things like user engagement, business process management, content management, authentication, and more.
The backend is thefoundation. It is done last of all for certain requests from the application, including promptly reworking after it has been raised.
The application itself is difficult to change because it is on the client-side. And the backend always remains in your power, therefore, the requirements for quality are lower, and for testing, and for the choice of architecture, and for optimization.