Where is the mount point and format of the iOS memory when it is plugged in a mac?
the iPhone does not present itself to any computer as a block device, so you won't be able to mount it and access the file system. This is among other things a security feature. Depending on what you are trying to change, you might be able to use iTunes for manually uploading music, playlists and I think possibly videos as well. Additionally you can use iTunes to upload files to any apps that allow it.

If you jailbreak your phone, you get full file system access at which point you can install an ssh daemon and ssh into your phone.