Both seems to mean "to enter". I had a feeling that the 入 is more "to put into" while the 进 is "to enter" ? But I also saw the "entrence" using 入.
2 Answers
入 (to put into/ to enter into)
进 (to advance/ to advance and enter)
进入 (advance into/ to enter) is a compound word
进(advance) is the main verb
入(into) is the resultative/ directional verb particle
As far as I have seen, personally, I see 入口 used as a noun, and 进 used as a verb.