first name vs forename

first name and forename both are nouns.

Word	Noun	Adjective	Verb	Adverb
first name	Yes	No	No	No
forename	Yes	No	No	No

As nouns, first name and forename are synonyms defined as:

Other synonyms of first name include given name.

first name (noun)	forename (noun)
the name that precedes the surname	the name that precedes the surname