Blizzard
In addition to the bonuses it provides, most pieces of equipment can show on your character, letting you look the part of your profession. When you perform a profession-related action, your character will visually swap into this profession equipment, then switch back again upon entering combat.
For the time being, transmog will not be supported with profession equipment, keeping the visuals displayed directly connected with what you have equipped. We recognize that as more types of equipment are discovered over time, there will almost certainly be a desire for transmog support with this equipment as well.