As far as I know a patent works as follows these days:
(1) you file your idea and pay them (a lot of) money 'administration costs'. The patent office will NOT check if someone else had your idea already.
(2) If at some point someone copies your idea you can start a lawsuit, needing more money but you have good chances to win IF your patent was written good enough to stand the lawsuit and exactly fits the case you try to fight
(3) If someone can show at any moment (that is, after you filed the patent) that your patent idea already existed and was published/patented before your patent was filed (even if you published yourself before filing the patent), your patent is void and you loose your investment
(4) A patent has only limited validity, both in area (other countries need a separate patent, of course with separate payment etc) and in time (I think after 5 years the patent expires, unless you pay a lot extra money to prolong the patent)

In short, as far as I can see a patent is highly bureaucratic stuff, you need to be at least a lawyer or something to get the patent nailed down to perfection so that it can held up in a lawsuit.