Should a DVD player able to play DVD-R, be able to play +R?

Question

And what does the R stand for?

Answer 1

Depends on how old the DVD player is.
Panasonic was notorious for not supporting +R on their DVD players; however, now it supports it.
On the front of the DVD player it should have logos with all formats it supports

Answer 2

recordable
yes it should
but early on the -r had the better of the compatibility with older dvd players