True or False: A respondent refers to a relatively small number of people selected to represent a sample, which is the entire group of interest.
That one is definitely false.
A respondent is a single individual in your sample, specifically someone who actually answered your survey questions. (Typically you can't get everyone in your sample to answer your questions. The proportion who do is called the response rate.) A respondent would never be a group of people. Sometimes we might use a larger unit of analysis such as a city or a country; but we wouldn't call those "respondents".
The sample is the group of people (or like I said, cities, countries, etc.) that you actually gather data about. It is contrasted with the population, which is the entire group that you're interested in. The population is what you really want to know about; the sample is what you gather data on. Typically the sample is much smaller than the population---maybe you have a sample of a hundred people to study a population of millions. There are exceptions, especially for large units of analysis: For some econometric studies of different countries the sample and the population are the same thing.