The Samsung Galaxy S4 is packed full of features, one of which has been present on earlier Samsung Galaxy models. That feature is the ability to connect the phone to a larger HD display with a HDMI cable and special HDMI/MHL adapter.
Whilst there are complete wireless sharing options available the cable solution is generally more cost-effective and flexible.
The S4 will continue this useful function, but there is a new HDMI adapter for it.
Part code ET-H10FAUWEGWW (shown in the image) will allow you to do the above, but the benefit is that it supports the MHL 2.0 standard meaning there will no longer be the need to connect power to the adapter.
Whilst this is still to be confirmed the presence of a microUSB port on the adapter would suggest that this cable will be compatible with the Samsung Galaxy S3 and Note 2, albeit with a power cable connected. It could also mean that the port acts as a USB host, meaning that other accessories can be connected via the MHL adaptor.