The focus of a sentence is what the sentence says about the topic.

Focus is a grammatical category that determines which part of the sentence contributes new, non-derivable, or contrastive information.

More info: http://en.wikipedia.org/wiki/Focus_%28linguistics%29

Juos okat hasim kanom vek katom? Did you see a grey dog or a cat? Okat hasim kanom. I saw a grey dog.
Juos okat hasim kanom vek hasim katom? Did you see a grey dog or a grey cat? Okat hasim KANOM. I saw a grey DOG.
Juos okat hasim kanom vek neqrim kanom? Did you see a grey dog or black dog. Okat HASIM kanom. I saw a GREY dog.