Now that you know what a chaise is, it should be pretty clear how they differ from a traditional sofa. Each piece of furniture is designed for sitting, but a sofa is designed to be sat on in an upright position, with knees bent and feet on the ground. Conversely, a chaise lounge is meant for sitting a more reclined position, with the legs straight and feet up off the ground. However, we believe you can choose your own position based on what makes you comfortable.
Additionally, sofas tend to be much larger than a chaise as a chaise is truly just a long seat whereas a sofa comprises multiple seats. A sectional sofa will even often have a chaise attached to it. A standard sofa can have a chaise as well.
Furthermore, sofas can come with arm rests on both sides or no arm rests at all, whereas a chaise will typically have only one arm and then an open side to lay into.