Non-probability sampling is a technique where researchers select samples based on subjective judgment rather than random selection, making it useful for qualitative research, exploratory studies, and when faced with time or budget constraints. Key types include convenience, quota, judgmental, and snowball sampling, which provide faster and more cost-effective results but may not accurately represent the entire population. While statisticians prefer probability sampling for its random selection and reduced bias, non-probability sampling can yield quality insights if applied correctly.