The S stands for serotonin and the N stands for norepinephrine and RI stands for reuptake inhibitor. So, obviously these drugs are supposed to work on both serotonin and norepinephrine. However, some literature uses SNRI to mean Selective Norepinephrine Reuptake Inhibitor, and this will work better on norepinephrine. Then you have the SSRI which is Selective Serotonin Reuptake Inhibitor, which works better on serotonin.

Norepinephrine-dopamine reuptake inhibitor

Cymbalta is an antidepressant that is in the class of serotonin and norepinephrine inhibitor. Wellbutrin is also an antidepressant, but in the class of dopamine and norepinephrine reuptake inhibitors.

Effexor (venlafaxine) is an SNRI or serotonin norepinephrine reuptake inhibitor.

No, it is a selective norepinephrine reuptake inhibitor.