The main difference is that with a 12 month experience, you can only take the G1 road test and get a G2 license and with a 24 month experience you can take the G2 road test and get a G license.
You can see the restrictions on a G2 license at http://www.mto.gov.on.ca/english/dandv/driver/gradu/index.shtml but unless you are still in your teens, the most important one is that you have to maintain a zero alcohol level. You are not allowed to drive after 1 or 2 beers or glasses of wine as you could if you had a full G license.
You will also lose your license at a lower number of demerit points if it is a G2 instead of G. You can read about that at http://www.mto.gov.on.ca/english/dandv/driver/demerit.shtml
I don't know if Ontario is the same but in Alberta, you are also not able to get a truck, bus or taxi license unless you have first gotten an unrestricted regular license.
You can see the restrictions on a G2 license at http://www.mto.gov.on.ca/english/dandv/driver/gradu/index.shtml but unless you are still in your teens, the most important one is that you have to maintain a zero alcohol level. You are not allowed to drive after 1 or 2 beers or glasses of wine as you could if you had a full G license.
You will also lose your license at a lower number of demerit points if it is a G2 instead of G. You can read about that at http://www.mto.gov.on.ca/english/dandv/driver/demerit.shtml
I don't know if Ontario is the same but in Alberta, you are also not able to get a truck, bus or taxi license unless you have first gotten an unrestricted regular license.