// Get a link to download a file
// By default, link's validity is limited to 2 hours and restricted to current user session

$file = get_entity($file_guid);
$download_link = elgg_get_download_url($file);

// Get a link to display an icon
// By default, link's validity is limited to 1 year and can be reused outside of the current user session

$icon = new ElggFile();
$icon->owner_guid = $owner_guid;
$icon->setFilename("path/to/icon.jpg");

$icon_link = elgg_get_inline_url($icon);