The SAP Business One Service Layer is an application server that provides web access to SAP Business One services and objects.
- It provides an easy-to-use, new generation REST (Representational State Transfer) API for consuming SAP Business One data.
- It is built on core protocols, such as HTTP and OData, and provides a uniform way to expose full-featured business objects.
- It supports OData (Open Data Protocol) for data access and supports JSON (JavaScript Object Notation) data format.
- It uses the Apache HTTP Server (or simply Apache) as the load balancer and ensures high availability for data access.
- It is easily scalable and provides high performance using parallel processing.
- It supports Basic and OAuth authentication schemes, which provides secure and seamless access to SAP Business One data.
The Service Layer aims to make it easier to develop web and mobile applications for SAP Business One, and to help customers innovate using new technologies and platforms.
As a developer, it is critical to understand the SAP Business One Service Layer and its architecture.

Understanding this will help you to more seamlessly integrate other applications with SAP Business One, and build applications that perform efficiently and reliably on top of SAP Business One.
Refer to this video to learn more about the Service Layer architecture.