Difference between population and sample
A population is a collection of people, items, or events about which you want to make generalisations. It is not always convenient or possible to examine every member of an entire population. For example, it is not practical to count the number of weeds in a paddock of wheat, however, It is possible, to count the number of weeds in a small area of the larger paddock. The entire wheat crop is the population, this subset of the population is called a sample.
A sample is a subset of people, items, or events from a larger population that you collect in order to generalise the results across the population. To represent the population well, a sample should be randomly collected and collection range should be adequately large and represent the whole population.