What statistics is for

Describing and inferring.

Two jobs

Descriptive statistics summarises data you have. Inferential statistics reasons from a sample to a population you cannot measure. The second is where the difficulty lives.

Every summary throws information away on purpose.
The question is always whether it threw away the part that mattered.

Population and sample

The population is everyone you want to describe; the sample is who you measured. Almost every mistake in the field is treating one as the other.