AWS OTA for ESP32

I'll answer your questions the best I can in the order you've asked them.

1. description for files used in project

I'm not sure whether you're asking for a description of the files present in any one of projects given the Amazon FreeRTOS repository or if you're looking for an explanation of the files you need for a generic project. Can you clarify here?

I would recommend you look at the FreeRTOS developer documentation on source file organization. I realize this doesn't perfectly match the AWS FreeRTOS source code structure, but given that AWS FreeRTOS is heavily influenced by FreeRTOS, it should give you some helpful background.

2. flow of program for OTA

AWS IoT Over-The-Air updates generally have the following steps:

1. Generate new firmware to upgrade to
2. Upload the firmware to the cloud (this is usually S3)
3. Sign the firmware image
4. Create an AWS IoT OTA job
5. This job is then picked up by the device which will download the OTA file, check the signature, and install the update when requested.

For more detail, see the OTA documentation