Imagine you have two text files, one with a list of names and another with a list of birth dates, which each name corresponding to the date of birth on the same line number in the other file, like so:

names.txt
Anthony Kiedis
Flea
Chad Smith
John Frusciante
dob.txt
1-Nov-1962
16-Oct-1962
25-Oct-1961
5-Mar-1970

You would like to join these files together into one file with the format <name>:<date_of_birth>. In linux, this can be done with paste, like so:

paste -d':' names.txt dob.txt

Here, -d is the delimiter option. This specifies which character separates data from file 1 and file 2. Running the command above produces this output:

Anthony Kiedis:1-Nov-1962
Flea:16-Oct-1962
Chad Smith:25-Oct-1961
John Frusciante:5-Mar-1970