several vs some

several and some both are adjectives.

Word	Noun	Adjective	Verb	Adverb
several	No	Yes	No	No
some	No	Yes	No	Yes

several (adjective)	some (adjective)
distinct and individual	(quantifier) used with either mass nouns or plural count nouns to indicate an unspecified number or quantity
considered individually	remarkable
(used with count nouns) of an indefinite number more than 2 or 3 but not many	relatively many but unspecified in number

several (adverb)	some (adverb)
	(of quantities) imprecise but fairly close to correct