Who are Kevali's and how they are different then Tirthankars?

Kevali – are those who have eradicated four defiling (ghäti) karma, but they are not tirthankars

1. Jnänavarniya (Knowledge obscuring) 
2. Karma, Darshanävarniya (Perception obscuring) karma
3. Mohniya (Deluding) Karma
4. Antaräya (Obstructive) Karma