YA vs. NA
I know there has been a divide recently in the young adult (YA) category as some books have become a bit more mature. Thus, new adult (NA) was born! New adult lives in a space between YA and adult and although it exists mainly for contemporary, it of course, can extend to other genres as well.
YA books are typically for late middle school – high school aged readers (and the characters within the books tend to reflect this as well). The content GENERALLY* does not veer towards being too mature. Think: kissing, making out.
NA books typically are for more college, early to late twenty aged readers (and the characters within the books tend to reflect this as well). The content GENERALLY* does become more mature and the steaminess level of these books is much higher. Think: sex scenes.
I hope this helps to distinguish some of these books and the age they are probably most appropriate for!