Many people don’t know the difference and some use these terms interchangeably. There is a big difference between these two powerful lifts. The squat is a more knee dominant movement, placing great demand on the quadriceps. The deadlift is a hip dominant movement, requiring strength and mobility of the posterior chain of your body and less demand on the quads. They are both great lifts for strengthening your whole body, however which one you do depends on the training goal, and the particular goal for each training session.
In the deadlift, the hips shift backward first, with some knee bend. This loads up the glutes and hamstrings as well as the quads. Since you are holding onto a weight, it also engages your upper back and your muscles for your grip, not to mention your core is engaged because it connects your upper back to your hips. It’s a practical lift for everyday life. What kills me is when someone has awesome form on a deadlift, and then they set the weight down by rounding their back. Rounding your back under a load = bad. The deadlift is all about keeping your low back arched and your shoulders back, aligning the spine in a position that won’t hurt it under load. The deadlift is also a foundation to learn other exercises such as the kettlebell swing or the Romanian deadlift also called a straight leg deadlift.
In the squat, your hips move down first, creating an end position where your lower leg and torso are parallel to each other if you took a picture and extended lines out from those segments of your body. It uses the same muscles as the deadlift, but in a different way. The knee bends to a greater angle and the load is more on the quads. The upper back is either supporting something or holding something up near your shoulders, different than pulling up on something like in a deadlift.
I often hear from clients that before they worked with me that their back or knees hurt when doing a squat or a deadlift. Doing a deadlift or a squat doesn’t hurt you, your form hurts you. Unless there is an underlying orthopedic problem, it is always due to poor form. I cannot emphasize enough on learning the right technique.