There are four basic types of probes; passive, active, differential, and current measuring. Passive probes are standard with scopes and contain no active devices, only passive. They are physically and electrically robust and can handle very high voltage typically. Passive probes are very rugged mechanically, but the bandwidth is limited typically to 500MHz. Using a 500MHz probe at 1GHz, will create problems. Active probes are optional, they are based on transistor devices and are powered by the oscilloscope. They are not as robust as the passive probes, but are able to achieve much wider bandwidths and have much lower capacitance, typically less than 1pF. They are ideal for probing high frequencies.