Which type of poll is unreliable because the people who respond do not reliably represent the total population?

Self-selected polls, such as those conducted through online surveys or call-in methods, are often unreliable because the respondents choose to participate voluntarily. This can lead to biased results, as individuals with strong opinions or interests are more likely to respond, while those indifferent or less engaged may not participate. As a result, the sample may not accurately reflect the broader population's views or Demographics.