of a population that has some characteristic using a random sample from that population.
By testing the claim, we mean making a decision as to whether we believe the claim is true or not based on the information provided by the sample.
In the terminology of hypothesis testing, we want to decide whether the null hypothesis is true. If we decide it is true or, more precisely, that we do not have enough evidence to support the idea that it is false, then we accept the null hypothesis.
If the assumption that the null hypothesis is true makes it very unlikely that we would obtain the sample we have, then we reject the null hypothesis.