To describe the love of your life, or even more than that. Your world would turn into complete darkness or turn upside down without her.
It is in the opening sentence of Lolita the novel by Vladmir Nabokov / Lolita the movie, in which the narrator was obsessed with his stepdaughter which he named Lolita.
It is adopted by Lana Del Rey as lyrics in her song "Off to the races".
She is the light of my life, fire of my loins, I'm dead when she leaves me.
Loginfo: noun
the information you need to gain access or log into a database, online account, computer, software, network, etc. Loginfo typically includes a user name and password, but may also contain additional information, such as PIN numbers, and secret questions and answers. Loginfo is the easy way to say "login information".
Honey, do you remember the loginfo to our bank account?
Man, I hate it when my computer crashes and I lose all my loginfo.
I lost my loginfo and now I can't check my emails.