The phrase "mule loafers" refers to a type of slip-on shoe that combines the characteristics of mule shoes and loafers. It means shoes that are easy to slip on and don't have a back or lace-up closure. Full definition
The way it's styled here is usually the way I wear it (tucked into high rise jeans and paired with mule loafers), but I've even worn it out for date night with ankle boots or block heeled sandals. (blog.natalieborton.com)