Language files

Language files are located inside the /languages plugin directory. Its structure is simple:

/languages
	default.pot
	team-booking-en_US.mo
	team-booking-en_US.po
	team-booking-it_IT.mo
	team-booking-it_IT.po
	team-booking-sv_SE.mo
	team-booking-sv_SE.po

As you can see, there are some translations bundled already, and there will be more upgrade after upgrade.

If your WordPress site language is set to English (American), then WordPress automatically picks up the en_US files. If your site language is Italian, then it picks up the it_IT files, and so on.

What if there are no .po/.mo files for your current site language? In that case, the plugin reverts to default internal hardcoded strings (English) and the .po/.mo files are not loaded at all.

There is also the default.pot file, which is the base for any custom translation.

Whether you wish to change some strings in an bundled translation (i.e. from "Book now" to "Confirm"), or make a new translation, you'll need to put your new files in a specific directory of your site in order to prevent your changes to be wiped out by a plugin upgrade.

That directory should be:

wp-content/languages/plugins