What is this warning? : Warning: _() expects exactly 1 parameter, 2 given in /ho

Hello,

I am new to wordpress, please can you tell me what this means?

Warning: _() expects exactly 1 parameter, 2 given in /home/greentes/public_html/wp-content/themes/chapter8/functions.php on line 109

Line 109 has the following (from functions.php):

‘description’ => _( ‘The welcome area in the content column on the front page.’, ‘simple-pfolio’ ),

It has this warning, many times for functions.php. _( is on every line, where this warning occurs.

Thanks ??