This is an opamp. It's by definition a voltage amplifier.
Voltage Delta Gain = Vout / Vin
You don't compute Iout/In in an opamp.
http://Cair to explain the difference then?
Most opamps have limited output current drive. You can use their outputs to drive another opamp, or a simple high impedance circuit.
But their outputs aren't beefy/strong enough to drive for example a 600 ohm load output transformer... and then several feet of cable behind that transformer's secondary. They're going to get hot and just break down.
There are special opamps that have more current output drive that can drive these transformer loads. Or you can tack on a discrete transistor booster circuits at the end of the opamp to increase its drive capability.
So now you have a high current output driver, but still operating at unity (Voltage Gain = 1) (depending on resistor values/ratio).
You don't call this beefier opamp as having "current gain"... That's implying there is a proportional relationship between it's output current and the input current you feed into it.
If you look at the datasheet for opamps having high output current capability, you'll find in the datasheet it's IOut (Output Current), example +/-26mA, and the load at which it's tested RL=600ohm, Vs=+/-17V.
If you look at a simple/typical opamp datasheet, you won't find this spec listed.
edit:
Here's a 250mA high-speed, high output current buffer opamp. BUF634
Unity Gain, voltage gain=1. They don't call these opamps "current amplifiers" (or having current gain) just because it has a higher output current drive capability.
The BUF634 is a high speed unity-gain open-loop
buffer recommended for a wide range of applications.
It can be used inside the feedback loop of op amps to
increase output current, eliminate thermal feedback
and improve capacitive load drive.
For low power applications, the BUF634 operates
on 1.5mA quiescent current with 250mA output,
2000V/µs slew rate and 30MHz bandwidth. Bandwidth can be adjusted from 30MHz to 180MHz by
connecting a resistor between V– and the BW Pin.