This is an expansion/modification of the Innate Invulnerability damage variant on the ICONS Wiki. In essence, all characters get Damage Resistance equal to half their Strength level (rounded down) but that resistance applies only to bashing and blasting damage, slashing and shooting damage is unaffected. This reflects the greater resistance sheer Strength grants when it comes to taking a beating, without necessarily making the character more physically impervious to harm. Regular Damage Resistance, granted by powers, protects against all types of attacks, unless the power has a specific Limit, and the higher of the two levels applies.
Example: The Mighty Saguaro has Strength 9 but no Damage Resistance power. He still gets Damage Resistance 4 (9 divided by 2 = 4.5, rounded down to 4) against bashing and blasting damage, but slashing and shooting attacks do their full damage against him. His only benefit from Strength there is his higher Stamina total. On the other hand, All-Star has Strength 10 and Damage Resistance 8, so he gets no extra benefit; his powers grant him more Damage Resistance than half his Strength level. If, for some reason, his Damage Resistance was nullified, but not his Strength, All-Star would still have Damage Resistance 5 (half of 10) against bashing and blasting damage.