Mars One's final goal is to establish a permanent human settlement on Mars. Currently, Mars is the only planet we know of that could feasibly support human life. We must be concerned with our future as a species, especially considering Earth may not last as long as we hope - so it is important that we have a backup plan. This is why it's important that humans take the first step to become a multi-planetary species. Mars One has arleady started contracting established aerospace companies that will be able to develop the required systems. Everything requires design, construction and testing, but no major scientific breakthroughs are required to send humans to Mars and to sustain life there.
There will be several unmanned missions that will be completed leading up to the main goal in 2023 - getting human life to sustain on Mars. This will make sure the environment on Mars is safe, as well as provide the hardware needed to build the settlements, for the first group of trained crew and civilians.