What is flebitis ?

You mean phlebitis?: Phlebitis is an inflammation of a vein with a clot. There are 2 species of phlebiti (i think i made that word up). Superficial thrombophlebitis affects smaller veins and is annoying at best. Deep vein thrombosis affects larger veins and is a medical emergency, as dvt's can send clots off upstream to the lungs and can be fatal.

Venous inflammation: Generic and somewhat old term to describe inflammation of a vein. It does not speak of if the phlebitis is in a superficial vein(less dangerous) or in a deep vein(dvt). This is an important distinction.