OpenTelemetry is an industry wide protocol created, to denote the standard template of adding distributed traces (primarily) and metrics / logs into any application.
The cost of monitoring applications has been shooting up over the years for teams. OpenTelemetry makes it easier for teams to avoid vendor lock-ins (by being tied in to their instrumentation SDKs) and switch providers.
A project “OpenTracing”, was released around 2014-15 by some folks including creators of Google’s distributed Tracing project, Dapper. Back in 2017, Google started a project “OpenCensus” to automatically capture traces and metrics from services in applications.
After this, both of these projects were merged together and donated to CNCF by those that were leading the development efforts.