It is a synonym for OP_RETURN.
This part is wrong. A better approximation is OP_RESERVED. If you have OP_RETURN, then the Script is invalid immediately. But in case of OP_RESERVED, it can be wrapped in some unexecuted OP_IF, and it will still remain valid.
But in general, it would be even better to compare it into "OP_FALSE OP_VERIFY", because this is what was intended, when creating OP_RETURN.
Edit: By the way, there were more pages like that in the past:
https://en.bitcoin.it/ScriptSo, I wonder, if we need a new one. If so, then some information from the link above can be useful. But maybe it is easier to update the wiki instead?