My brief summary recollection(hopefully correct):
USB-C is a physical connector type. That is pretty much it, it’s a physical connector. but obviously a connected cable needs a communication standard (what is sent on the wire/cable).
Here’s where it gets tricky. When you say “USBC”, Contemporary tech naming, currently, says that is the USBC connector with USB 3.2 communication standard (USB4 is around).
Thunderbolt is not a physical connector standard, it is a communication standard. It uses the USBC physical connector within the Thunderbolt standard — or I believe thunderbolt 3 and 4 only use USBC (?).
Obviously the hardware inside the connected devices will need to include Thunderbolt capability. Also, USB I believe is an open standard. Thunderbolt is owned and licensed by Intel.