APIs are a way for developers to access data from third-party sources. You can use the APIs to build apps or websites that connect to other systems. Developers do not only use APIs to create applications that interact with other systems. They're also useful for businesses who want to integrate their own services with others.
Any tailoring of documentation or upgrade of software can be implemented in a better and effective way. Thus, this leads to the improvement of the lifecycle of software as well as its quality.