Here is a great summary by a local lactation consultant group: http://www.ailc.ca/levels-of-lactation-support.html
Another (US-based) summary: https://uslca.org/wp-content/uploads/2015/05/Whos-Who-Short1.pdf
A very detailed description of all lactation support credentials: http://uslca.org/wp-content/uploads/2017/07/2-page-Whos-Who-updated-July-2017-Watermark.pdf