Does restore backup replace what's already in my iOS device?

I backed up my iPhone and I'm going to restore backup on my new iPad because I want to move some things to it so I could continue. But will it erase the content in my iPad.

Added (1). I mean that the apps or everything else I already have in IPad will be erased if I restore backup.

Yes, all the existing data in your iPad will be erased when you restore your device with previous iTunes Backup. But if you use a third-party app to extract and export the backup files to the computer first and then transfer the exported files to the new iPad, things will change! You will find the detailed solutions in the following page.