Can't seem to find an explanation for why joins are denoted as left/right or Inner/Outer. If I know why it would probably help me remember which is which.
This article seems to have a pretty good explanation of the various joins. This article has a handy table to show you how the various joins operate and where to use them.
It's a visual thing. Look at a Venn diagram that shows two overlapping circles. the place where the circles intersect is "inner", the left circle is what you get with a left join and the right circle is what you get with a right join.