What's the meaning of the word ------14 AMPS ?

This word relating to the electric nail gun /staple/tacker, thank you very much.

An electronic device that increases the voltage, current, or power of a signal

The AMPERE (shortened to AMP) is a measure of electrical current. On a device like the example you have, it tells you the current that the device draws at the rated voltage (V).

An AMPLIFIER (also shortened to AMP) is a device, as singlemom says, that increases the amplitude of a signal.

I believe you are asking about the first case.

Thank you for the answer given, I under stand now and I study english hard for my job.