If the first digit is 0 it's a manager position and falls under skill type 0, level not important.
If the first digit is not 0 but the 2nd is 1, then it's a skill level A
If the first digit is not 0 but the 2nd is 2 or 3, then it's a skill level B
Those above are the ones that you can count your work experience for points on an FSW application, jobs you can get an AEO for, jobs that is easy to immigrate with if you are on a temporary work permit etc.
There are also low or semi-skilled jobs:
If the first digit is not 0 but the 2nd is 4 or 5, then it's a skill level C
If the first digit is not 0 but the 2nd is 6, then it's a skill level D
Those jobs above would not let you immigrate except if you get certain jobs allowed under the BC or AB PNP's and then you'd have to go in on a temporary work permit and work for 6-9 months before being able to apply for PR with employer support.