Selection or assignment of groups of people instead of individual respondents, based on membership of a group, location or some other identified variable, is labelled as

Selecting groups of people rather than individuals, by membership, location or another identified variable, is cluster sampling.

The population is divided into clusters and whole clusters are then chosen.

Location sampling is not the standard term for this procedure.

Stratified sampling draws individuals from every stratum, not whole groups.

Collective sampling is not a recognised sampling method.

Multistage cluster sampling selects clusters within clusters in successive stages.