This passage is referring to a US Citizen petitioning for his/her spouse. Upon receipt of the Permanant residency card (Green card), it is considered conditional for Two years after issuance.
Essentially, the spouse gets the "permanant" card, but in reality it is a Temporary/permanant residency card. The spouse can still have the permanant residence card revoked if all the normal conditions are not met. For example, if you get divorced before the two year period, the card can be revoke even though it is supposed to be permanant.
The underlying point is that you must stay married for two years after the spouse receives the permanant residence card. I dont think it matters how long you have been married prior to that date.
In your circumstance this would apply after you first get your green card/citizenship. You would then petition your wife, and when she is granted the green card, it is conditional for two years.
Some people here have said that you can petition for your spouse with a green card, and some say you have to be a full citizen..I am not 100% positive.

