allows developers to focus on the frontend of their applications and leverage backend services
Backend-as-a-Service (BaaS) allows developers to focus on the frontend of their applications and leverage backend services without building or maintaining them. BaaS and serverless computing share some similarities, and many providers offer both, but the two models have several differences.
Think of developing an application without using a BaaS provider as directing a movie. A film director is responsible for overseeing or managing camera crews, lighting, set construction, wardrobe, actor casting, and the production schedule, in addition to actually filming and directing the scenes that will appear in the movie. Now imagine if there was a service that took care of all the behind-the-scenes activities so that all the director had to do was direct and shoot the scene. That's the idea of BaaS: The vendor takes care of the 'lights' and the 'camera' (or, the server-side* functionalities) so that the director (the developer) can just focus on the 'action' – what the end user sees and experiences.
BaaS enables developers to focus on writing the frontend application code. Via APIs (which are a way for a program to make a request of another program) and SDKs (which are kits for building software) offered by the BaaS vendor, they are able to integrate all the backend functionality they need, without building the backend themselves. They also don't have to manage servers, virtual machines, or containers to keep the application running. As a result, they can build and launch mobile applications and web applications (including single-page applications) more quickly.
*Server-side refers to everything that is hosted on or takes place on a server instead of on a client in the Internet client-server model.