I'm not sure how yours is cut but I presume the 5 are

1 no straps
2 regular two straps
3 halter - use only one strap - they should be longer than usual straps.
4 straps cross between shoulder blades to compensate for cut away armholes or just to stop straps slipping.
5 longer lenth of the straps allow them to fix to the front, over the shoulder, cross below the back fastener then come around and fasten in the front. For deep v backs.