An API is a set of routines, protocols and tools for building software applications. In other words, an API specifies how software components should interact. Financial Institutions, specifically banks, are either outsourcing their own IT staff (developers, to be precise) to either build an API or an aggregator to compile incoming data and create services to better serve customers, or, they (banks) are striking partnerships with marketplace APIs and indirectly with third party applications that these APIs support.