Samsung 4ch 720p HD 4 Cam Security System

are these cameras powered over ethernet (poe) or do they each require a power adapter and power source?

From the buyer: They use a power adapter. No POE for this.

Do these transmit wirelessly, or do I have to wire them to the DVR unit?

There is an option for these to be transmitted to your DVR wirelessly, but you will need a Samsung Wi-Fi adapter that is not included in the sale.