What is the difference between a node, stage, and step in Jenkins pipelines?

The concepts of node, stage and step are different:

• node specifies where something shall happen. You give a name or a label, and Jenkins runs the block there.

• stage structures your script into a high-level sequence. Stages show up as columns in the Pipeline Stage view with average stage times and colours for the stage result.

• step is one way to specify what shall happen. sh is of a similar quality, it is a different kind of action. (You can also use build for things that are already specified as projects.)

So steps can reside within nodes, (if they don't, they are executed on the master), and nodes and steps can be structured into an overall sequence with stages.

It depends. Any node declaration allocates an executor (on Jenkins master or slave). This requires that you stash and unstash the workspace, as another executor does not have the checked out sources available.

Several steps of the Pipeline DSL run in a flyweight executor and thus do not require to be inside a node block.This might be helpful for an example such as the following, where you need to allocate multiple nodes anyway:

stage("Checkout") {  checkout scm}stage("Build") {  node('linux') {    sh "make"  }  node('windows') {    bat "whatever"  }}stage("Upload") {  ...

Another (maybe more realistic example) would be to allocate multiple nodes in parallel. Then there's no need to let the stage call be executed in another allocated executor (aka within node).

Your example looks good to me. There's no need to allocate multiple nodes within the single stages, as this would be only additional overhead.