Hi AJW,
I think that probably "Yield" has been mentioned to you with reference to a financial benefit. Normally people talk of "rental yield", this is the amount in figures or as a percentage that the property will earn over a year. It is normally quoted before any costs are taken out (taxes, mortgage payments, community fees,etc).
I hope I have the right end of the stick, and it is not some strange gadget that keeps the roof on!
Good luck and feel free to send me a private message (PM) if you have any further questions.
Jamie