function wpskills_custom_user_profile_fields($user) {
  $output = '';	
  $output .= '<h2>'.__("Custom user profile fields", "text-domain").'</h2>';
  $output .= '<table class="form-table">';
    $output .= '<tr>';
    $output .= '<th><label for="hobby">'.__("Hobby", "text-domain").'</label></th>';
      $output .= '<td>';
        $output .= '<input placeholder="'.__("Hobby", "text-domain").'" type="text" name="hobby" id="hobby" value="'.esc_attr(get_user_meta($user->ID, 'hobby', true)).'" class="regular-text" /><br />';
        $output .= '<span class="description">'.__("What is your hobby?", "text-domain").'</span>';                    
      $output .= '</td>';
    $output .= '</tr>';
  $output .= '</table>';
  echo $output;
}
add_action('show_user_profile', 'wpskills_custom_user_profile_fields');
add_action('edit_user_profile', 'wpskills_custom_user_profile_fields');

// Save Custom User Profile Fields
function wpskills_custom_user_profile_fields_save($user_id) {
  if (!current_user_can('edit_user', $user_id )) {
    return false;
  }
  update_user_meta($user_id, 'hobby', $_POST['hobby']);
}
add_action('personal_options_update', 'wpskills_custom_user_profile_fields_save');
add_action('edit_user_profile_update', 'wpskills_custom_user_profile_fields_save');