frequency
Frequency counts how often a repeating wave repeats, that is, how many complete cycles happen each second. A slow wobble is low frequency; a fast buzz is high frequency. It is the wave's pitch.
Frequency f is measured in hertz (Hz), one cycle per second. It is the reciprocal of the period T (the time for one full cycle): f = 1/T. So a wave with a period of 20 milliseconds has f = 1/0.02 = 50 Hz. Mains is 50 or 60 Hz; audible sound spans about 20 Hz to 20 kHz; radio runs into megahertz (10^6 Hz) and gigahertz (10^9 Hz).
Almost everything reactive depends on frequency: a capacitor's and inductor's opposition, filter cutoffs, resonance, and antenna sizes all scale with it. Note: angular frequency omega = 2 times pi times f (radians per second) shows up in the formulas because one cycle is 2 times pi radians around the circle. It is the same frequency in different units, not a new quantity.
Middle A on a piano is 440 Hz: the string vibrates 440 times per second, a period of 1/440 = about 2.27 ms. An octave up doubles it to 880 Hz.
Higher frequency, higher pitch.
Higher frequency is not the same as higher amplitude. A wave can be fast and faint or slow and strong; frequency and amplitude are independent.