Dependent and independent samples

What is actually the difference between a dependent sample and an independent sample (paired or unpaired samples)? And why is it important to know the difference? Whether the data are from a dependent or independent sample determines which hypothesis test is used.

If your data are independent, for example, a t-test for independent samples is calculated or an analysis of variance without repeated measures. If your data are dependent, for example, a t-test for dependent samples or an ANOVA with measurement repetitions is calculated.

The online statistics calculator:
https://datatab.net/statistics-calcul...

The tutorial about dependent and independent samples
https://datatab.net/tutorial/dependen...