besides vs too

besides and too both are adverbs.

Word	Noun	Adjective	Verb	Adverb
besides	No	No	No	Yes
too	No	No	No	Yes

As adverbs, besides and too are synonyms defined as:

Other synonyms of besides include also, as well, likewise.

besides (adverb)	too (adverb)
making an additional point; anyway	to a degree exceeding normal or proper limits
in addition	in addition