If you restore your iPhone 4 from the phone, will it permanently erase eveything?

I'm selling my iPhone 4, and I want all my personal information gone off there, and I don't want anyone else to be able to access it in the future. I watched a video on YouTube that said you can wipe all your information off you iPhone 4 by going into Settings > General > Reset > Erase All Content and Settings. Will doing so permanently reset my iPhone 4 to factory settings, and wipe off all of my pictures, videos, call history, apps, internet history, ect, with no chance of anyone getting to it? If not, how can I completely and permanently reset my iPhone 4? Thanks.

Added (1). Here is the link to the video in case you need to see it:

Unfortunately, no. This will erase the majority of your information, but if you want ABSOLUTELY everything to be off, you should plug your phone into iTunes then choose restore on the summary page of your iPhone. This is the sure way to go get it emptied to factory settings, not just erasing all content and settings. This process can take a good ten-fifteen minutes, but is worth it as you won't have to worry about any of your information again.