upstream vs service

[tirelibirefe]

Hello,
I'm a newbie for apisix and trying to understand the concept.
Yes, I've read the documents but I didn't understand.
When I install httpbin, is its service an upstream or a service in Apisix terminology? If it is a service, what is upstream? If it is an upstream, what is service?

Thanks & Regards

[guitu168]

There is a one-to-one correspondence between services and upstream. To be precise, httpbin itself is a service, but it acts as an upstream of Apache APISIX.