Amplitude is the maximum voltage reached by the signal. It is measured in volts, V.
Peak voltage is another name for amplitude.
Peak-peak voltage is twice the peak voltage (amplitude). When reading an oscilloscope trace it is usual to measure peak-peak voltage.
Time period is the time taken for the signal to complete one cycle. It is measured in seconds (s), but time periods tend to be short so milliseconds (ms) and microseconds (µs) are often used. 1ms = 0.001s and 1µs = 0.000001s.
Frequency is the number of cycles per second. It is measured in hertz (Hz), but frequencies tend to be high so kilohertz (kHz) and megahertz (MHz) are often used. 1kHz = 1000Hz and 1MHz = 1000000Hz.
time period =
Mains electricity in the UK has a frequency of 50Hz, so it has a time period of 1/50 = 0.02s = 20ms.