Generally, any software application has some kind of backend logic that gets deployed on the server to be accessible through the internet. In case of big enterprise-level applications such as Banking or Finance, it may be worth to manage a server or cluster of servers. However, in case of small applications or the application where you want to execute certain logic depending on some user events, such as data changes in database or on API requests from mobile app or a web application, managing a server may be an overhead in terms of efforts as well as cost. However, when you use the Firebase platform, you don't need to worry about it as it provides Cloud Functions that lets you run code based on events emitted by specific Firebase products without managing servers.