Domino REST APIs make the data in Notes databases available in a way that it can be used by any application, server, or middleware that speaks HTTP(S). Let's take a look at a few examples.
An engineering company stores the security data sheets of their products in a Notes database. These sheets contain information about the hazards of the products and the necessary safety precautions to take. Using Domino REST API's, all this information can be available on a web application, allowing someone who doesn't have access to a Notes client to view the security data sheets on the web.
A software consultancy firm uses a Notes application for travel approval. The workflow requires the consultants to raise travel requests in the system, which are then approved by the managers. Without Domino REST API, the approving manager needs a computer with a Notes client installed on it to take action on the request. Domino REST API's allow you to build mobile applications that allow the managers to process the requests on their mobile devices. The Domino REST API's grant access to managers to approve, reject, or comment on requests.
Integration with other apps
An organization maintains their presentation decks in a Notes application. The customer sales representatives use these presentations when meeting with customers. Without Domino REST API the representatives switch between the Notes application and Salesforce when preparing for the presentation. With the Domino REST API's, data from the Notes application can be integrated into Salesforce. Then, sales representatives have a single view of sales-related data in Salesforce and presentation decks in Domino, saving them time and making them more productive.
Integration with third-party companies
An organization processes applicants for various third-party companies. They may have different levels of experience and provide data with varying levels of data quality. With Domino REST API's, the organization can allow REST API access for the third-party companies, confident that data verification or data fixup will not delay processing of the applicants.