| Generally used to mean one or both of these options. Expanded out, it might read And Or Or. But that's way too hard to say.
I have in the past been convinced that in the case of X and/or Y, you could either have X and Y or Y, but maybe not just X. I confuse myself sometimes. Then i'd say "You know what they mean!" and give up. Never try to apply logic to colloquial english structures, especially if your logic is feeling feeble that day. | 
