Originality refers to created or invented works that can be characterized as being new or novel, and thus can be distinguished from existing works. An original work is one created with a unique style and substance.
The term "originality" is often applied as a compliment to the creativity of writers. The approximate opposite being a wholly derivative work.
The concept of originality is largely culturally contingent. Originality started to become the ideal for Western culture around the 18th century. When Shakespeare was creating his works it was common to appreciate not the differences so much as the similarity with an admired classical works. Shakespeare himself avoided "unnecessary invention".