I am not sure what you mean. Do you mean the categories for skilled worker? You can see them at http://www.cic.gc.ca/english/information/applications/skilled.asp and it says that for Category 2, you need to have arranged employment. When you read the links I gave you about AEO, you will see that it is only given for a skilled job, skill type 0 or skill level A or B.
To find out which skill type or skill level a certain job fits into, you have to find the job in the NOC at http://www5.hrsdc.gc.ca/NOC/English/NOC/2006/OccupationIndex.aspx Once you find the exact NOC code of 4 digits, you can tell from the code what it is. You can see the instructions for that at http://www5.hrsdc.gc.ca/NOC/English/NOC/2006/Tutorial.aspx#6
For example, NOC 2281 is a skill level B job. This you can see because the first digit is not 0 or it would be a skill type 0 job. When the first digit is not 0, then you look at the 2nd digit. If the 2nd digit is 2 or 3, it's a skill level B. If it is 1, it would be a skill level A.