A larger sample can yield better results. But, there is a cost involved for every respondent, in direct costs to conduct the survey and the time invested in their response. It is not always practical, or necessary, to ask everyone what they think.
If you choose to sample, a Sample Size Calculator can help. Here are a couple you might find useful. Each provides simple definitions for the terms used.
On top of what is “right” statistically in terms of sample size, you should also consider these other factors when determining sample size…