My forte is not explaining things well in English so here is a quote from a well known site:
Every rhombus has two diagonals connecting opposite pairs of vertices. Using congruent triangles, one can prove that the rhombus is symmetric across each of these diagonals.
from the BBC website:
A rhombus has four equal sides and also has its opposite sides parallel. It is formed by joining two identical isosceles triangles base to base.
Its diagonals are not equal but cut each other in half at right angles. Both diagonals are lines of symmetry.
If you have 2 die there are only a limited combination of rolls that will give you numbers 2 and 12 (two 1's and two 6's respectively). The number 7 uses the most combinations of dice than any other number.
This website may help you understand better - or confuse you!