What classifies a volcano as active or inactive?
It all depends on the time its been since the volcano last erupted.
If a volcano erupts "often", meaning it erupts every couple of years, then it's active.
But if a volcano hasn't erupted in around 10,000 years, then it is inactive and not expected to erupt.
But there is another type of volcano called a dormant volcano. This is an active volcano that hasn't erupted in over a decade, but is expected to erupt again.
Someone please check my answer, not too sure.
Hope this helps :)