The terms jackets and sleeves frequently get interchanged but it's important to know the difference. Think of the jacket like the one you wear, it's outter wear. The jacket is the outter most packaging of your record. The sleeves are inside the jacket and actually hold the record. In some cases, mainly 7"s folks will choose to just use a sleeve in place of a jacket but sleeves are always paper while jackets are cardboard. Inserts are sometimes confuse folks as well, they don't hold anything they just give you more space to show your art or a great way to present liner notes or lyrics.