What is the difference between deadlifting with your feet spread very far apart as opposed to having your feet at shoulder width?
What happends when you do different stances on the the deadlift it's pretty much like doing a wide and narrow grip bench, it hits the primary muscle in different ways. Basically, it applies different pressures to your back.
*just make sure if you're using a mixed grip switch up which hand goes over and which goes under the bar when you lift
Very wide,arms inside legs:Sumo stance.More hip and leg emphasis.
Narrow stance:More lower back emphasis.
Sumo also helps to decrease range of the movement. Allowing a weight to be moved a shorter distance.