Here string (herestring)

A single word need not be quoted:

$ LANG=C tr a-z A-Z <<< one
ONE

In case of a string with spaces, it must be quoted:

$ LANG=C tr a-z A-Z <<< 'one two three'
ONE TWO THREE

This could also be written as:

$ foo='one two three'
$ LANG=C tr a-z A-Z <<< "$foo"
ONE TWO THREE

Multiline strings are acceptable, yielding:

$ LANG=C tr a-z A-Z <<< 'one
> two three'
ONE
TWO THREE

Note that leading and trailing newlines, if present, are included:

$ LANG=C tr a-z A-Z <<< '
> one
> two three
> '

ONE
TWO THREE

Here strings are particularly useful for commands that often take short input, such as the calculator bc:

$ bc <<< 2^10
1024

$ read -r a b c <<< 'one two three'
$ echo "$a $b $c"
one two three