An API allows external programs to communicate with and access data from an internal software program. APIs enable data exchange between websites, applications, and organizations while keeping the underlying data in the same location. Applications created using APIs that combine and visualize data from different sources are commonly called "mashups." Some examples of mashups include ones related to transportation, crime, and food that make existing data more useful.
2. What is an Open API? An API provides a mechanism by which external programs can communicate with an internal software program and even access or exchange data. APIs allows data exchange between websites, applications and organizations, while the data source remains in the same place. (Source: www.web2fordev.net). APIs are more flexible and powerful than RSS feeds.
3. What is a mashup? Applications built using APIs are commonly called ‘mashups’ – combine data and functionality from different programmes. Mashups (usually) are about: Combination Visualization Aggregation In a mashup, the emphasis is on making already existing data more useful.
For instance, APIs let you grab statistics from a website and use them on your own website. That way one does not have to access individually other websites, but can instantly combine data from different websites (Source: www.web2fordev.net).