The two terms don’t mean the same thing.
There’s some ideological overlap, but it’s fuzzy. There are some people with one foot in each of the two camps (I used to be one of them; now I’m not), which can be confusing.
If there lines of separation that are even slightly bright, I’d say they are these:
- Most, if not all, left libertarians are anarchists. Most, if not all, liberaltarians consider the state at least inevitable and possibly necessary; and following from that,
- Most, if not all, left libertarians eschew electoral politics and “public policy,” while most, if not all, liberaltarians consider those two things part of their program of action.
All of the above is, of course, just my opinion.
That is all.