What is the difference between an echocardiogram and an ultrasound test?

Same. An echocardiogram is an ultrasound of the heart. Ultrasounds can be done for other organs such as the kidney.
Same machine . Same machine. Different exam and usually a specialty ultrasound probe. Echocardiogram is specific to an exam of the heart. Ultrasound is a generic term used to describe looking at virtually any body part using this technology.