Airflow is how much air is moved without any restrictions. Static pressure measured in mmH2O refers to how high a column of water can be pushed by the pressure of the fan. Higher is better. dB or DBA refers to the intensity of sound and the scale is logarithmic and not linear. Basically, a rise in 10dB is a perceived doubling of loudness.
These specs are useful especially when there's nothing else to rely on but there's little to no regulation on how they're measured between manufacturers. Take these specs with a grain of salt and stick to benchmarks and in-depth reviews with standardized testing whenever possible.
If you're interested in new fans and would like recommendations, list your specs, where you're shopping / located, budget, and what kind of features you're looking for.