What does || mean in Erlang? -

i found there || in list manipulation. || mean? there examples ||?

lists:sum([a*b || {a, b} <- foo]).

it used in list comprehensions. list comprehensions shorter way create lists without having use funs, maps or filters.

if have list l:

l = [1,2,3,4,5].

and want double every element, can do:

lists:map(fun(x) -> 2*x end, l).

but list comprehensions can do:

[2*x || x <- l].

Expalin