RMS:
the average continuous power output an amplifier is capable of producing; power output an amplifier can produce consistently over extended lengths of time. RMS power contrasts to peak power, which is used for brief moments in order to recreate sudden, high-energy sounds (transients). RMS power can be produced continuously for the length of time the amplifier is in operation. It is the most important of the two power ratings (RMS versus peak) when researching an amplifier.
RMS is technically the average value of a particular waveform. When we say an amplifier has power output of some RMS figure, then we mean that amplifier is able to produce on average a certain amount of power. If you looked at a sine wave you would see a series of hills and valleys. The peak of the hill would be peak power. RMS measures the average area under the outline of the hill and its corresponding valley. RMS is a way of averaging the total waveform.
Note that RMS Power is equal to RMS Voltage multiplied by RMS Current. The term RMS is often used in audio to refer to continuous power output; however, RMS is not technically a power term since it applies to waveforms. However, you will hear RMS referred to most often relating to power .
PEP:
The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions.
Not the best explanination but I hope it helps a little
