The first letter of a Canadian postal code identifies a province, or
part of a province:

A = Newfoundland
B = Nova Scotia
C = Prince Edward Island
E = New Brunswick
G = Eastern Quebec
H = Metro Montreal
J = Western Quebec
K = Eastern Ontario
L = Central Ontario
M = Metro Toronto
N = Southwestern Ontario
P = Northern Ontario
R = Manitoba
S = Saskatchewan
T = Alberta
V = British Columbia
X = Northwest Territories
Y = Yukon Territory

In the second position (the first number), a 0 indicates that the postal
code is for a whole post office, usually indicated for rural communities.
The 6th character (last number) is also usually a 0 in such cases (as
in L0M 1S0). All addresses for the community have that postal code,
whether these are rural routes, postal boxes or in some cases, smaller
towns with letter carrier routes.

Other numbers for the 2nd position indicate the postal code is in a larger
urban community with letter carrier service. The postal code is thus precise
enough to identify street blocks, particular rural routes or groups of
postal boxes.

Canadian postal codes are always separated into two blocks of three characters.
The first three characters are the Forward Sortation Area (FSA), an
“area code” used to identify a district. The last three characters thus
identify the block, postal box set, or post office within the FSA.

Some special Canadian FSAs: K1A is for federal government activities in Ottawa;
M7A represents the Ontario provincial government, G1A represents the
Quebec provincial government.