What does the idiom R and means?

There's no idiom called "R and". It's possible you're thinking of a different idiom or phrase. Could you please clarify what you mean?

For example, are you thinking of:

* "R and R" which stands for "rest and recreation", typically used for military personnel.

* "R&D" which stands for "research and development", referring to activities related to innovation and new product creation.

If you can provide more context or the full phrase you're trying to understand, I can help you better!