Deepstack poker tournaments are basically tournaments where the starting amount of chips is far bigger than the blind level.
For example, in a more conventional tournament you start with 1000 chips and have a initial blind level of 10/20, this means that you have 50 big blinds. On the other hand, in a deep stack tournament you would start with more like 5,000 maybe 10,000 chips with the same blind level potentially giving you 500 big blinds to play with. Furthermore, in a conventional tournament you would expect to see blind levels increase every 10-15 minutes whereas in a deep stack tournament you are more looking between 20-30 minutes for blind increases.
This means that a different sort of strategy is needed for deepstack tournaments, you are better off waiting to be dealt a premium hand, if you do this you can then pile the chips in when you do catch a premium hand.
In every sense a deepstack tournament is identical to a freezeout in structure all that changes is the time between blind increases and the amount of starting chips.