Well, the simple answer is no, your iPad is not a backup for your iTunes. However, whatever music you may have on you iPad should anything happen to your laptop may potentially be retrieved with the right software. Generally speaking, it is the other way round and your iPad is backed up on your laptop. This is not necessarily the case though, since the current iOS allows you to choose to backup your iPad to iCloud instead. iCloud backups do not include your music or video, but any music you buy on iTunes is available to download again any time you like. iTunes Match gives more online backup options, but to cut a long story short if you want to backup all your music and videos, then you should go for an external storage option, or you could alternatively get an account with Dropbox or similar and keep your music & video in your Dropbox folder so it is automatically backed up online. I use a Time Capsule from Apple, which in conjuction with Time Machine, backs up my entire hard drive automatically every night.