That's correct - it's a square where on one axis, the paternal allele (allele = one of the possible forms of the same gene), and on another the maternal allele is listed. Often, it's also indicated whether an allele is recessive or dominant.
Then, in the table that results, all the possible "combinations" of allele between the paternal and maternal party are created. If you count how often a certain combination appears, it indicates the likelihood of that combination.
See the picture (though it is directly from Wikipedia, please note). The likelihood of BB is 25%, of Bb is 50%, and of bb 25%.
