Does ios 5.1.1 Delete my texts, pictures, or my apps and their data?

I want to update my iPhone 3GS 32GB (never jailbroken) to ios 5.1.1, and i get this message: Updating to iOS 5.1.1 will backup and restore the apps, media, contacts, calendars, notes, text messages, and settings on your iPhone.

What does it mean by backup and restore? Does it mean it will delete it?

Once you sync your iphone to your itunes library, your data should be automatically saved. When you update your iphone it will be restored and wiped which is why you have to sync your iphone again after the update to get all of your apps, media, contacts etc back onto your phone. Information like texts and contacts should always stay on your sim card