Iguana (, ) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America\
My next door neighbor had an Iguana as a pet.  I don't know why.  You can't cuddle with an iguana!  
Two species are included in the genus "Iguana": the green iguana, which is widespread throughout its range and a popular pet, and the Lesser Antillean iguana
Theirs must be a green iguana, then.  I'm scared of them.  Do they bite humans?
The green iguana is also known as the American iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus
Is there an ecological advantage to iguanas?  What do they eat?
sure! thats because they  iguana feeds almost exclusively on algae and large males dive to find this food source, while females and smaller males feed during low tide in the intertidal zone.