What are text domains for in WordPress?

Question

WordPress

Hello! I studied the plugin code on wordpress and came across the following a couple of times: A
line from the plugin declaration A
* Text Domain: personalize-login
line from the plugin code
'title' => __( 'Вход', 'personalize-login' )
Googled it. It turned out that this is a text domain. But what he gives us and could not understand. Hope you can explain. Thanks in advance!

Answer 1

This is to localize the plugin into other languages. The domain is needed in order to identify translatable plugin strings in any translation systems (po-edit or codestyle localization for example).
The construction is as follows: __("Translated word", "Domain"). That is, by default, the word "Login" will be displayed. And in the case the site language will be English, for example, and the plugin has the appropriate localization file - instead of it, "Enter" or "Sign in" will be substituted. Well, or how it will be translated.