Some-Some-Of | Commonly Confused Words

Some of

/sʌm əv/

A phrase indicating an unspecified part of a whole group.

This word has no synonyms

/sʌm/

An unspecified amount or number, or a few individual things or people.

The conductor passed by and Clifford gave him some money.'I must try some,' she said.At the same time he liked him some.

Some is a standalone word used when referring to an unspecified amount or number.
Some of is used when referring to a part of a specific group or quantity.
Think of some of as cutting from a whole, it implies a selection.
Some can be used with both countable and uncountable nouns without any determiner, whereas some of usually needs one.
Remember, some of always suggests a more specific reference than some does.