The 30-pin dock connector is the connector which was used for Apple devices like iPhone, iPad and iPod back since 2003 after discarding the Firewire connector used earlier by the initial 2 iPod models in 2001 and 2003. About a decade later Apple came up with the Lightning connector in September 2012 which is compatible with iPhone 5, iPod Touch, iPod Nano 7th Gen, iPad 4th Gen and the iPad Mini. Here is a small summary about both of them in order to make the users have a crystal clear concept for the two.
The Lightning connector is very convenient and is not so complicated for use as it contains a total of 8 pins in it unlike the older 30 pin dock connector and can be inserted into the device with either side up i.e. its reversible. Moreover it is approximately 1/4th of the size of the old dock which makes it handy. It is faster and so has the lightning term attached and it is claimed by Apple that data flows faster through the newer cable (which is again slightly thinner than the older one and is about 2 inches longer than the older one) attached to the connector. Also the USB end of the connector has a smaller housing than the earlier one.
This is an exact example of the fact that the up gradation of the gadgets in terms of technology has attracted and is beneficial for the users undoubtedly but has also adopted the newer trend of sleekness and compactness simultaneously.