The purpose of I-751 is to remove conditions of residency. Your marriage was under 2 years old when your wife received her green card - that's why the green card was for 2 years. You lift the residency conditions so she can get 10-yr green card which is unrestricted.
All green cards regardless of type are to be legal permanent resident of the US. The expectation is you'll be living and working in the US.
If you have never read the guide for new immigrants, now is the time to familiarize yourself with it: https://www.uscis.gov/sites/default/files/document/guides/M-618.pdf