Standard frequency crystals - use these crystals to provide a clock input to your microprocessor.
Rated at 20pF capacitance and +/- 50ppm stability.
Low profile HC49/US Package.

12MHz is good for use with devices that need USB.

32kHz means it is precisely half of a 16-bit counter.
Start counting at 0x8000 (or 32768). When the counter rolls over from 65535 to 0, then you know that exactly one second has passed.
Reset the interrupt, reset the counter, and start counting again! Rated at 12.5pF load capacitance, 35K ohm max (18K ohm typical) series resistance, and +/- 20ppm stability.
The 32kHZ is the Small cylinder package. All the others are the "normal" ones.