Differentiating between a gecko and a lizard usually becomes a problem when people fail to realize the fact that a gecko is a type of lizard which makes lizard the general name for this type of animal. Both belong to the same kingdom, phylum, class, order. The little difference between a gecko and a lizard starts when you consider the suborder part of their classification.
A gecko belongs to the Gekkota group, while other types of lizard belong to the four other groups in the suborder part of their classification. This simply means not all lizards are geckos, whereas a gecko can be referred to as a lizard.
Unlike geckos that are commonly found in regions with warm climates, lizards are found in every part of the world. Also, unlike geckos that feed mostly on insects, crickets, moths, butterflies, etc. lizards have more materials included in their diets, as there are some that feed on fruits, vegetation.