What is gettext?
gettext is the GNU internationalization system, one of the oldest localization toolchains still in wide use. Its model: source code wraps strings in a lookup function, traditionally _(), a tool called xgettext extracts them into a template (POT file), translators fill in per-language PO files, and those are compiled to binary MO files the runtime loads.
Two design choices define gettext. First, the source string itself is the key, so code stays readable and untranslated text falls back to the original. Second, the tooling is file- and pipeline-oriented, which made it a natural fit for open-source projects; WordPress localization, for example, is built on gettext conventions.
PHP has a native gettext extension, but most Laravel projects use the framework's own translator instead, which follows the same key-lookup idea with PHP array and JSON files. You will still meet gettext whenever you exchange work with translators, since PO is one of the formats every translation tool imports.
// PHP gettext extension
echo _('Save changes');
// Extraction (shell):
// xgettext --language=PHP -o messages.pot src/*.php