railway yard vs piece of land

railway yard and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
railway yard	Yes	No	No	No
piece of land	Yes	No	No	No

As nouns, piece of land is a hypernym of railway yard; that is, piece of land is a word with a broader meaning than railway yard:

railway yard: an area having a network of railway tracks and sidings for storage and maintenance of cars and engines
piece of land: an extended area of land

Other hypernyms of railway yard include parcel, parcel of land, piece of ground, tract.

railway yard (noun)	piece of land (noun)
an area having a network of railway tracks and sidings for storage and maintenance of cars and engines	an extended area of land