SECOR refers to Small Employer Certificate of Recognition. If your company hires less than 10 employees you would fall under this category.
MECOR refers to "Medium Employer Certificate of Recognition". If your company hires 11 - 30 employees you may need this certification. It will depend on your certifying partner. For more information on MECOR CERTIFICATION
COR refers to Large Employer Certificate of Recognition. Companies with more than 10 employees at any given time
In Alberta, as well as other Canadian provinces it is becoming common place for businesses to have to acquire their Certification in order to secure their contracts with large employers. In order to acquire your certification you need to partner with a certifying partner. COR/MECOR/SECOR partners are in all the different industries. Depending on which partner you choose, you will have to follow their requirements to achieve and retain your certification. You must check with your partner as to what their requirements are. The basic steps to becoming certified can be found here.
The "All Partners- Pdf" explains which industry each partner serves in Alberta.