What does DOB stand for? 

DOB stands for Date Of Birth. 
DOB-DOB stands for Date Of Birth.

 What is DOB means?  

DOB is the short form of Day Of Birth commonly known as DOB in daily life as a short form. The word DOB is always used in the document. 

in every document your CNIC or passport anywhere where the date of the birth option is required they mention that what is your DOB so we can understand that the meaning of the word.    

What is the DOB number?

 DOB is actually your date of birth number. which shows your birth date, month, and years through this your age can be calculated by month, date, and years as well.