Here are some great terms regarding your wedding dress necklines to become familiar with:
High - collar just brushing the chin.
Sabrina - a high, slightly curved neck.
Queen Elizabeth - the high collar stands up in the back and comes to a closed V in the front.
Jewel - fabric encircles the natural neckline.
Square - neckline is shaped like half of a square in the front and may be the same in the back or high and straight.
Sweetheart - the front neckline is shaped like the top half of a heart with the back being higher and straight across from shoulder to shoulder.
Off the Shoulder - the neckline falls below the shoulders and hovers above the bustline (but the dress has sleeves).
Boat (or Bateau or Scoop) - the neckline gently follows the curve of the collarbone almost to the tip of the shoulders in the front and the same in the back.
Queen Anne - the neckline rises high at the nape (back) of the neck, then sculpts low in the front either in a sweetheart shape or to outline a bare yoke.