What is the functions of LLC and MAC sub layers of Data link layer? Why IEEE 802 splits the OSI Data Link Layer into two sub-layers?

Actually, original ethernet header i.e 802.3 is known as MAC[ Media Access Control ]  layer. But that header doesn't have any field to represent the encapsulated protocol inside frame / don't have any field to identify the upper layer protocol. Just to represent the encapsulated data or upper layer protocols one new layer is added i.e LLC [ Logical Link Control ] Layer. 

-> MAC layer contains source mac, destination mac and length field.

->LLC layer is TYPE field actually.