What is the difference between traceId and requestId in tracing?

I am developing with microservices oriented architecture and want to trace. I was googling and I found that istio for example has the fallowing headers:

x-request-id
x-b3-traceid
x-b3-spanid
x-b3-parentspanid
x-b3-sampled
x-b3-flags
x-ot-span-context

Mainly I want to know the differences between x-request-id and x-b3-traceid, but ok if someone could share the others headers

Solution

Istio is using envoy, I think you can find your answers on this docs https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/headers#id13