Before you watch this video you should really watch the previous video in the section which covers Types of Inheritance.
Pedigrees are graphical representations of ancestry with respect to one or more disease(s). Males are represented with a square while females are represented with a circle. The shape is black/filled in if the individual is affected by the disease. The shape is empty/white if the individual is not affected by the disease (may be unaffected or carrier). Usually each generation (row) is labeled with a roman numeral while each individual is labeled with a number.
Autosomal Dominant Pedigree
Autosomal Recessive Pedigree
X-Linked Recessive Pedigree