The Uno supports interrupts on every pin via the pin-change interrupt mechanism,
as well as the two "external interrupt" pins D2 and D3. Pin change interrupts have
the granularity of a port, not a pin, so you have to write code in the handler
to investigate what change happened.
To detect human input an interrupt is overkill, its much neater just to look at
the pin with digitalRead() in loop().
Interrupts are useful when dealing with frequent or urgent events (think 1kHz
or above, microseconds).