Here's the breakdown:
* Gho represents the sound of "f" as in enough.
* Oti represents the sound of "i" as in women.
* Gh represents the sound of "f" as in rough.
So, theoretically, "ghoti" could be pronounced "fish", but it's not a real word and isn't a valid spelling. It's just a clever way of showing how illogical English spelling can be.