Where Does iTunes Store the Backup?

Did the latest update, but got an error message and the iPhone was a brick with a picture of the transfer cord and iTunes symbol. I had backed up all the settings and data before the update, but could not restore the phone on my desktop where I originally attempted the update.

Had a prior update and backup on my laptop, so I restored the phone on it, but the data was months old. I want to get the backup file off my desktop and insert it on my laptop so I can restore my phone to the latest data back up.

Where is the backup file and what is named?

Thanks!