Hi!! And welcome to the boards!! DD stands for Darling Daughter (or Disney Daughter, or Dear Daughter). DH is Darling Husband (or whatever, we won't go there!!LOL) etc. etc. It just makes it easier when you are typing. Don't worry, after awhile you will get the hang of it. Sometimes I still have to stop and think when I see an abreviation!
OH LOL is Laughing Out Loud!!
TTFN (Ta Ta For Now) OK the snow has really gotten to me!!!