yaml files in jenkins pipeline

Just started out working on jenkins, among other things I'm trying to understand the role of yaml in pipelines. I understand that pipelines or declarative pipeline (do other type of pipelines exist in jenkins?) are defined using a syntax that is based on an extension of groovy and that yaml can be used along with some plugins or extended library to generate an on the fly groovy-based pipeline definition. Is my understanding correct?

The blog post you linked to in your comment which describes using YAML to generate Pipelines is about an unofficial 3rd-party Jenkins plugin which adds this feature; neither native Jenkins nor official plugins support using YAML to generate Pipelines.

pipelines or declarative pipeline (do other type of pipelines exist in jenkins?) are defined using a syntax that is based on an extension of groovy

There are two types of natively-supported Pipelines: Scripted Pipelines (which are pure Groovy scripts) and Declarative Pipelines (which use a Groovy-based DSL).

StackExchange DevOps Q#11916, answer score: 1