tracking vs trailing

tracking and trailing both are nouns.

Word	Noun	Adjective	Verb	Adverb
tracking	Yes	No	No	No
trailing	Yes	No	No	No

As nouns, tracking and trailing are synonyms defined as:

tracking and trailing: the pursuit (of a person or animal) by following tracks or marks they left behind

tracking (noun)	trailing (noun)
the pursuit (of a person or animal) by following tracks or marks they left behind	the pursuit (of a person or animal) by following tracks or marks they left behind