Apache Thrift's architecture can be viewed from two angles. The first approach shows the tool that is used by the developer—the Thrift compiler—along with the set of instructions that determine what to do in order to run the services.
The second way is to get to know the internal architecture and the purpose of protocols, transports, services, and processors that the developer will use, in order to know how the tools are built and what are the ways of their operation.
As in every craft, you can build things knowing the basic operation of the tool that you will work with; not every developer needs to have a deep knowledge of Apache Thrift's internals to do his job. However, to fully understand how it works and design the scalable and performant services and system architectures, this knowledge is essential.
If you wish to get the information about Apache Thrift IDL syntax and start preparing your services right away without getting too much into the technical details...