What does it mean to connect to LDAP'y?

Question

PHP

I don’t fully understand the LDAP domain
There is a wonderful package for Laravel --> AdLdap2-Laravel https://github.com/Adldap2/Adldap2-Laravel
$this->adLdap->connect(null, $user_dn, $password) --> I took this construction from an example.
What does this connection to Ldap'y through PHP (Laravel) mean?
I rewrite from the native implementation (the ldap-extension is used
there) Everything is done there with ldap_bind($connection,$user_dn, $password)
But even when I wrote natively, I don’t understand what this connection means and for me this is some kind of magic.
Somewhere I think in the direction of authorization there, but what does it give ...