Lead was used for writing in Roman times. The 'lead' in a pencil is a mixture of graphite and clay. It is called lead because when the graphite deposit was first discovered in Borrowdale, England, the locals thought it was lead (or plumbago). Chemists later corrected them but the name has stuck.

Graphite is a form of carbon, like diamond, but softer.

Unlike lead, graphite is non-toxic.

Lead and graphite are two entirely different materials.
Lead is a heavy and dense metal; it is soft, malleable, and melts at a low temperature. It is also toxic.
Graphite occurs naturally and is a form of crystalline carbon.
Though people often refer to a lead pencil, the lead in the pencil is in fact graphite.

Graphite is a form of Carbon, so its carbon in lead graphite. Notice that lead itself is a different element but the term "lead graphite" is generally used for that black substance which makes the "lead pencils".

Note that there is no lead in lead pencils, its carbon, in the shape of graphite.

you would find graphite A.K.A black lead in pencils occasionally some paints

Because if pencil doesnot have graphite,we cannot write anything.In pencils,the black element is graphite used to write anything.