LDO is an acronym for Low-DropOut - this is a type of linear voltage regulators with (surprisingly) low dropout, or minimal voltage drop between input and output.
Yes, 3.3V are much more common, it's better to use them (nevertheless 3.6V is still possible). In fact, you can use any voltage regulator within specified range.
Also as I understood from this particular range, this module perfectly suits for Li-Ion batteries, because their voltage ranges are almost the same.