Ampere

The Ampere or "Amp" is a measure of electrical current flow. It measures the amount of electric charge past a point per second. We often refer to devices by how many amps they draw, and power service is rated in amps.
Many devices, motors especially, tend to require more amperage to get started then they need to continue working. For this reason, it is important to know if the an amperage rating is "peak" or "continuous" for a device.
Amperage is something that must be closely monitored in many electrical systems as having excessive amperage flowing through a conductor (wire) creates the potential for that conductor to melt or vaporize often creating a fire hazard or worse. This also leaves the electricity that was on that wire with nowhere to go, opening up the potential for electric shock or electrocution. Because of this, properly rated circuit breakers or fuses are always a must. Circuit breakers and fuses are rated to handle a certain amperage before breaking the circuit in a safe manner. There are many types of circuit breakers and fuses out there for different applications, and a professional should be consulted when installing / choosing one.
In the famous equation V=IR, I is typically current measured in amps.