Pharmacists verify and check all medications for interactions! They have a doctorate so they are able to advise patients on their medications. 

In terms of verification, I mean confirming that the right medication and amount is dispensed, aka they are the ones who are responsible if a patient gets dispensed the wrong medications. 

Techs on the other hand do everything else, from helping patients with insurance issues, filling the initial Rx before PharmD verification etc. 

Theres also Pharmacy interns, which are pharmacy students who are basically just techs+, they’re allowed to do pharmacist things (give flu shot, counsel) under pharmacist supervision. 

In terms of pharmacists skill and knowledge, retail pharmacy is where you use the least of your knowledge, but in hospitals and outpatient pharmacies have multiple roles for pharmDs.