Every one of them if I google them have prior answers that would be hard for me to improve on.
That said I am running into folk that are very new to the web. We're not born knowing how to research but you should take this time to head to google and see what has been written so far.
There's also been a spat of spammers that re-post old questions. We're never sure why they do that.
What does web content migration mean?
Moving content from one site to the other?
Does it mean deleting the old site?
Does it mean transferring the URL?