Hertz (Hz)
The basic unit of measurement of frequency. It is a measurement used to denote one complete occurrence of an event in one second.
The frequency of a crystal is measured in megahertz (MHz) or kilohertz (kHz). In Kingtronics we usually usd KHz.

Frequency
Measured in Hertz (Hz), it is a periodic repetition of an event within a unit of time.
In an electrical circuit, it is the number of times a resonator plate oscillates or vibrates in one second. The most common herts for Kingtroncis QKT is 32.768KHz

Frequency Tolerance
Often called Calibration Accuracy, it is the amount of frequency deviation from the specified nominal frequency at room temperature (25°C).
This term is expressed as a minimum and maximum percent (%) or parts per million (ppm). Kingtronics can provide -20℃~+70℃, -40℃~+85℃, -10℃~+60℃

Load Capacitance
A capacitance, specified in picofarads (pF), presented to the crystal.
The parallel load resonant frequency (FL) is a function of the load capacitance.

For more details, please refer to below link, thank you.
www.kingtronics.com/quartz-crystals/
www.abracon.com/Support/qtzcry_glossary.pdf
www.abracon.com/Support/qtzcryoscil_glossary.pdf