Samsung Already Released Latest Flagship Phone,i.e., Galaxy S4 and Working on Note III Prototype.
We also have Samsung Galaxy S4 Active Which is much similar to S4 but There are some Changes that we have noted here:

galaxy s4 active

Galaxy S4 is Much Powerful & Beautiful but The Design is not new from Previous Series and Also it is concerned with its Plastic body.

The New Galaxy S4 Active is made and IP67 Certified.The Device is Simply Water-Proof(Up to 30 Minutes) and Dust-proof.
This was About Body,now let us get on Main Features:

Exterior Body & Panel:The Galaxy S4 Active has a ‘tough exterior body’ where the original S4 has a plastic body.

Primary Camera:The Galaxy S4 Active has an 8MP camera where the original S4 has a ‘13MP camera’.

Display Used:The Galaxy S4 Active has a TFT LCD display where the original S4 has a Super AMOLED display.

IP67 Certification:The Galaxy S4 Active is ‘Dust proof and water resistant’ where the original S4 is not

Weight:The Galaxy S4 Active weighs about 151 grams where the original S4 weighs about 130 grams.

This is Short Difference Between Both Phones,Both the Phones have their Own Advantages.
Simply We can say that,Galaxy S4 Made for Who Want a light Weight,High-End Smartphone and Galaxy S4 Active who want a high end smartphone, but can be used outdoors which is Water and Dust Proof.

Also Look At Galaxy S4 Mini Version