The target population is everybody the sociologist would desire to be able to generalise their findings to. In other words, if a researcher was hoping to reach conclusions about the whole population of the UK, then that would be their target population. It would be difficult to find a sample that would be representative of such a large population (although people conducting opinion polls, such as for general elections, do attempt this). As such target populations are smaller than this, preferring to focus on people in particular areas, of particular ages or in particular occupations (depending on the topic being researched). When creating a sample, most sampling methods require a sampling frame - a list of everyone in that target population (election pollsters would use the electoral register, for example).