Apara Vidya or its shortened from Avidya is knowledge of any sector or worldly knowledge in the wider sense.

Etymologically Avidya is the antithesis of knowledge, ie., the absence of knowledge. But the word is not used in the negative concept. All knowledge or Apara Vidya which envelopes the phenomenal world is termed Avidya. 

Isa - Upanishad explains the idea in the following verse:
Vidyam cha avidyam cha
yah tad veda upayam saha
Avidyaya mrutyum tirtva
Vidyaya – amrutam – asnute

It is through Avidya that one crosses the great stream of death while through Vidya one attains immortality.

Thus the Upanishads make it clear that the worldly knowledge (Avidya) which though ephemeral is also of importance to the seeker, absolute knowledge (Vidya) is of the higher self which helps him attain his goal.