2/$5 (for example): Get $5.00 off when you buy 2 items
$1/2 (for example): If you buy 2 items, you get $1.00 off
YMMV: Your Mileage May Vary = this deal may or may not work for you depending on your store, its policies and your coupons.
Blinkie: Those little coupon machines in the grocery store aisles that spit out a coupon for a specific product. These can also be found in CVS, Walgreens, Rite Aid, etc.
CRT: coupons that print out at the end of your receipt
Cat or Catalina: coupons that print from a separate machine when you check out.