I've been eying these pants for awhile. Some places call them soft pants, or silky pants or warmup pants My husband calls them soccer pants because they remind him of the zippered pants he wore before practice.
I call them comfy pants. I actually bought them right before going to Uganda -- I wanted something other than leggings to wear on the plane and decided that a pair of these were perfect. I bought them at Nordstrom Rack but I've seen them everywhere. Yes, they're loose and casual, but you can dress them up with flats or heels (or do what I did on the plane to home from Uganda -- pair them unwashed dirty feet in flipflops and three-day, greasy hair). It's up to you, really.
jacket: Nordstrom (similar)
pants: Nordstrom Rack (similar -- on sale!)