一些 / 有些【yìxiē / yǒuxiē】

一些 is "some, a few, a little" – an amount left unspecified. It goes before a noun, countable or not, with no other measure word.

有些: some of them

有些 + noun at the start of a sentence picks out part of a group and says something about that part, setting it against the rest. At the start of a sentence 有些 is the everyday choice; 一些 there sounds written.

有的 does the same job as 有些 and has its own point.

After an adjective: a bit more

一些 after an adjective means "a bit more": 好一些 "a bit better", 便宜一些 "a bit cheaper". After a verb it's "some more": 多吃一些. In both places 一点儿 can replace it and sounds more casual.

有些 before an adjective: somewhat

有些 + adjective or feeling means "somewhat, a bit", like 有点儿 but a touch more formal.

No other measure word

些 is itself a measure word, so 个 can't follow 一些, and 些 only combines with 一, 这, 那, 哪 and 有.

• × 一些个苹果 → 一些苹果
• × 三些书 → 一些书 / 三本书