To assist you in understanding military records, we have provided information from the Library and Archives Canada site for First World War Abbreviations Used in Personnel Records:
First World War Abbreviations Used in Personnel Records.
Abbreviation—Name.
In addition, the following links will lead you to further resources which will aid your understanding of the records:
http://regimentalrogue.com/misc/researching_first_world_war_soldiers_part2.htm
http://www.bac-lac.gc.ca/eng/discover/military-heritage/Pages/military-abbreviations.aspx
http://www.associations.rafinfo.org.uk/acronyms.htm
http://www.1914-1918.net/abbrev.htm