1that one
2that thing
3that (as opposed to this)
4(used before a verb or adjective for emphasis)
5(euph.) menstruation
6sex
7also pr. nèi ge
8(used to humorously or indirectly refer to sth embarrassing, funny etc, or when one can't think of the right word)
9(used in speech as a filler, similar to "umm", "you know" etc)
Examples
nǐ你gèng更xǐ huan喜欢nǎ ge哪个，zhè ge这个hái shi还是nà ge那个？
你更喜欢哪个，这个还是那个？
Which do you like better, this or that?
那个穿棕色大衣的女人是谁？
Who is the woman in the brown coat?
去那个村庄的唯一途径是过河。
The only access to the village is from the river.