The different kinds of sampling

The different kinds of sampling?

In math, we have been covering different kinds of sampling such as unbiased (fair) and biased (unfair) and some of them I just don't have an idea how to classify them, do you have any hints to help you classify them?

Simple Random Sampling
Voluntary Sampling
Convenience Sampling
Stratified Sampling
Systematic Sampling

Anything that you do to remember the difference, please tell me, and if you're in no hurry or anything could you give an example of a couple of them? Thanks so much!