What is a difference in using | vs || to concatenate two columns?

Found the difference:
|| trims the column while | does not: for instance:
var1 = 'cat '
var2 = 'dog'
var1 | var2 => 'cat dog'
var1 || var2 => 'catdog'

Please let me know if there are other differences.

A single | is a soft concatenate, a || is a hard concatenate.

e.g.

Text1 = 'text     '
Text2 = ' more    '

Text3 = Text1 | Text2
Text3 will contain 'text      more    '

Text4 = Text1 || Text2
Text4 will contain 'text more         '

With a hard concatenate, the trailing spaces are shifted to the end of the expression. If you start using parentheses, you can control where the hard and soft concats happen.

e.g.

Text1 = 'text     '
Text2 = 'more     '

Text3 = Text1 || Text2
Text3 will contain 'textmore          '

Text4 = Text1 || (' ' | Text2)
Text4 will contain 'text more          '