reading vs poring over

reading and poring over both are nouns.

Word	Noun	Adjective	Verb	Adverb
reading	Yes	No	No	No
poring over	Yes	No	No	No

As nouns, poring over is a hyponym of reading; that is, poring over is a word with a more specific, narrower meaning than reading:

reading: the cognitive process of understanding a written linguistic message
poring over: reading carefully with intent to remember

Other hyponyms of reading include speed-reading, perusal, perusing, studying, browse, browsing, skim, skimming.

reading (noun)	poring over (noun)
the act of measuring with meters or similar instruments	reading carefully with intent to remember
the cognitive process of understanding a written linguistic message
a mental representation of the meaning or significance of something
a datum about some physical state that is presented to a user by a meter or similar instrument
written material intended to be read
a particular interpretation or performance
a public instance of reciting or repeating (from memory) something prepared in advance