Hey there !
If I am using FreeRTOS with TCP/IP, do I need an Ethernet connection for it to work?
Definitions time !!! TCP stands stands for “Transmission Control Protocol.” Long story short, it’s a protocol imposing how packets are transmitted.
Ethernet, It’s a technology for wired networking.
Take a look at this image (article source.) It presents the chain of transmission/reception of data. It’s named OSI. In this, TCP takes place in the “Transport Layer”, while Ethernet is on “Data Link Layer” and “Physical Layer”. What we can understand is that using TCP do not impose to use Ethernet. The implementation of these two technologies are not dependent. Ethernet can be replaced by Wi-Fi in this chain (not in a finger snap of course.) To go further, TCP can be replaced by another protocol as UDP (not in a finger snap, they don’t present the same pros and cons nor the same interfaces, but it’s not the subject.)
So First ! You do not need an Ethernet connection for it to work.
What does the TCP/IP extension make the device function as? What are its usecases?
I’m not sure of my answer, so I’ll preserve myself of spreading misinformation. Can I suggest you to take a look at the following resources ?
A post explaining the role of the device depends more on its funder API than on FreeRTOS :
A topic about using an ST MCU as a Wi-Fi Access Point (AP) :
FreeRTOS+TCP Example Projects and TCP networking tutorial from FreeRTOS website.
Happy TCP-ing !! 
