The caulking can be used for 'minor repairs'. The problem is it may not match in color to the existing mortar (so you'll EASILY see your repair work if you try to caulk a 'spot' that can 'catch the eye'. ALso, if it gets on the face of the brick, it will get in the pours VERY easily and is very difficult to remove. Hence, you'll see that too.
Mortar, on the other hand, requires much more work. It's not that hard but it is time consuming. If the weather is good and you have the time and patience, go for it! Here is a link to get you started - Repointing Brick If you need any specialized guidance, try contacting The Brick Industry Association.