I assume you are talking about Gustavus Adolphus. He standardized drills, equipment and tactics within his army. He also integrated mercenaries much better than his counterparts allowing them to fight more efficiently with his own Swedish troops. In terms of tactics he brought about the combined arms approach and built his army around that idea.

1. Linear formations for combat as opposed to the tercios favored by the Spanish and their variations. These were generally formed three deep allowing his armies to bring more firepower to bear. Also instead of having the front line fire and move towards the back, they would instead kneel and reload which would allow the next line to fire. By the time the third line fired, the first line would be ready to go again.

2. The Swedish army had a higher gun-to-pike ratio than other armies. Because they didn't form tercios, they had less pikemen. Because they had less pikemen they could arm more men with guns.

3. Smaller caliber artillery for increased mobility. All European armies fielded cannon but the Swedes essentially went down a caliber for every gun. While the Spanish carted around 12 and 6-pounders the Swedes used 6 and 3-pounders. The smaller cannon meant they could move together with infantry formations during combat.

4. Cavalry armed with swords as well as/instead of pistols. The caracole was fairly common cavalry tactic but it was very ineffective and slow. By re-arming the cavalry with swords they could then be used as the decisive arm of the army to deliver the final blow when needed.

The combined arms approach meant bringing all three arms of the army together. Cavalry would be used to screen and skirmish at first. Then the infantry would move forward while the cannons fired. Because the Swedes had more guns, enemy infantry would be "softened" more quickly. The cavalry, now regrouped, could be sent forward in a charge to shatter the enemy formation with the infantry and lighter cannon following up.

Source: The Age of Battles - Russell Weigly

EDIT: It should be noted that these innovations came about as a result of Sweden's socio-economic situation. Sweden in the 17th century was poor and had a tiny population, especially when compared to the large continental powers. Gustavus Adolphus wanted to be the defender of Protestantism but he knew that with the resources at his disposal he would be unable to wage war in the slow and costly fashion of the time.

I can't help but I know one person who can. Paging /u/VonAdler

If you're referring to Gustavus Vasa's Swedish Model it is because he was able to utilise a combined arms model of warfare that used all 3 traditional arms (infantry, calvary & artillery) offensively as well as standardising drill, weapons and doctorine within his army.

The Swedish counterparts during the day weren't significantly better or worse - just a little less efficient.

Source: The Art of War in the Western World - A Jones.