html - What is purpose of echo statement in the following php code? -

i new php. found following code snippet in tutorial while trying learn radio button. echo statement never gets executed( not see checked statement printed ever). purpose of echo statement?

<input type="radio" name="gender" <?php if (isset($gender) && $gender=="female") echo "checked";?>  value="female">female <input type="radio" name="gender" <?php if (isset($gender) && $gender=="male")  echo "checked";?>value="male">male 

in scenario if condition compare value of $gender. when value matches echo print "checked" attribute inside radio in html. radio button appear checked.

you can see view source.