What do (R) and (Z) mean in chemical names? So, I'm confused on the notation my professor uses in a certain question; could someone explain. 
He says: 

Draw the structure: (R)-(Z)-chloro-4,6,-dimethyl-3-octene 

I get everything after '(z)'

I'm just unsure what he means by '(R)-(Z)'... 

Any input is appreciated. Thanks.
The name (R,Z)-chloro-4,6-dimethyloct-3-ene is ambiguous. This could be (R,Z)-1-chloro-4,6-dimethyloct-3-ene, (R,Z)-3-chloro-4,6-dimethyloct-3-ene, (R,Z)-6-chloro-4,6-dimethyloct-3-ene, or (R,Z)-8-chloro-4,6-dimethyloct-3-ene. (2-chloro-4,6-dimethyloct-3-ene, 5-chloro-4,6-dimethyloct-3-ene, and 7-chloro-4,6-dimethyloct-3-ene have one additional stereocenter.) For example: