SOA (Service Oriented Architecture) is a process in the information technology which organizes different function in an enterprise application into a standard service that can be reused to meet the business needs.
The SOA infrastructure allows different applications to exchange the data with one another during the participation in the business process.
What makes SOA so important is the reuse of the business services. In other words, A code from an existing application can be exposed as a webservice and then can be used to meet the business requirements.
SOA allows clients and services to communicate with each other without concerned for the platforms they are running on.
Services in SOA are loosely coupled. There are very few dependencies between the application and the services.