DDLG stands for Daddy Dom, Little Girl. It’s a style of BDSM where the submissive woman enjoys being cared for by her Dom, in whatever form that takes. DDLG doesn’t always involve age play (one partner acting younger or older than they really are), but it may.
A Daddy Dom acts as a care giver, looking after his little. This contrasts with a more sadistic style of domination where the Dom takes pleasure in inflicting pain on his sub. In a DDLG relationship the dominants role is to nurture and look after his little, and ensure she is safe and growing as a person.
The articles on this website should help you understand all about this style of relationship, how to find a little, how to find a Daddy Dom and DDLG rules for your little.