一些 (yīxiē) indicates an indefinite quantity ('some, a few') before a noun. Unlike 有的 (yǒude), which singles out a subset within a group, 一些 simply describes an unspecified number. After an adjective, it means 'a bit more' (大一些) — similar to 一点儿 (yīdiǎnr), but 一些 is more general and often used for countable quantities.