Without Hox genes you'd be a very different looking person. They ensure that your head sits on the top of your body, that your feet are at the bottom, that your arms hang by your side and that your nose is in the centre of your face. They are the pattern forming genes that guide body plans.
Hox genes are highly conserved across most animal species and are DNA sequences that specify the anterior-posterior axis and segment identity of organisms as they develop. Hox is an abbreviation of homeobox, the name given to the region of DNA of 180 base pairs that codes for a protein domain called homeodomin. These are transcription factors that bind to DNA and regulate the transcription of genes. They are involved in a cascade of events that can turn genes "on" or "off."
A homeodomain protein binds to DNA sequences known as gene enhancers which can activate or repress a gene's actions. So for example, a Hox gene product may activate the gene inside a developing insect that will specify structures on its thoracic region, or a Hox gene product may repress a gene involved in the development of the antenna.
Hox genes are also sometimes referred to as homeotic selector genes.