We use "few" for things that can be counted and "some" for things that cannot be numbered. Therefore, we would say "few friends." We would say, "some water" There are many English speakers who pay no attention to this rule and use both words where "few" should be used.

"A few" usually means around 3-5. There is a number loosely implied. At some point in childhood, native English speakers learn to differentiate between "a couple" which means only 2, and "a few" which implies more than 2, but still a small number. "Some" does not imply a specific number, but more an indeterminate amount that more than a little and less than a lot. "I have some friends" could really be any number of friends, from a few to much more. It is important to note the difference between "a few" and "few", too. "Few" means "not many." "I have a few friends" means "I have about 3-5 friends" while "I have few friends" is a somewhat sad statement that means "I do not have many friends."

There are a few different ways to explain this, depending on how the words are used, in the way you used them, although both are 'indefinate' (not giving an exact number) they follow a hierarchy. This being couple: a couple meaning around 2, a few meaning around 3-5, several meaning around 7, some is usually between 7-10 mark. Other uses of 'some' would be someone, somebody, something and so forth.

"Some" is used as a determiner, meaning it is often being used for things that are "uncountable" and plural nouns. For example: I need some milk. While "FEW" can be said to give the idea of better than nothing or more than expected. For example: You don't need to go shopping, there are a few eggs left in the fridge. I hope these answer your questions.

Essentially both are the same. Personally I would consider "few" to be a lesser amount than "some" but that's just me.