barrier vs railing

barrier and railing both are nouns.

Word	Noun	Adjective	Verb	Adverb
barrier	Yes	No	No	No
railing	Yes	No	No	No

As nouns, railing is a hyponym of barrier; that is, railing is a word with a more specific, narrower meaning than barrier:

barrier (noun)	railing (noun)
a structure or object that impedes free movement	a barrier consisting of a horizontal bar and supports
any condition that makes it difficult to make progress or to achieve an objective	material for making rails or rails collectively
anything serving to maintain separation by obstructing vision or access