An experiment with phonetic writing

[ololololo]

Perhaps a transparent example---remembering that I do not speak French and cannot read a made-up representation of it in any event---might help

I brought it to you — the word “aujourd'hui”. You and the native speaker pronounce it the same way, but you don't know how to spell it. You write it down in your own way (oujuvie), and the speaker does it the right way (aujourd'hui). 
You will be able to communicate with the native speaker, but you will not be able to correspond with him, relatively speaking