"DVR" Digital Video Recording" is a timer that is set for a specific title on a specific channel. "Pass" evaluates program listing and if the keyword is found on any channel or any description, that program will be recorded.
ie; "DVR" would be to record the series "House" on the OTA Channel 10 on each Tuesday evening from 8-9pm. This can also be setup to record all new episodes.
"Pass" would be to record any show where either the title or description has the keyword "House" in it. Many shows would be recorded, "House", "This Old House", Haunted House" and also any program that has the word "House" in the description.