Similar to Male adaptor fittings, Female adaptors enable a connection from a pipe, hose or cable to another pipe, hose or cable which is a different size or type. But the Female adaptor connects pipes etc that have male threads. Female adaptors can be used to reduce the flow or even terminate the pipe, hose or cable run.
Currie & warner manufacture medium to large volume adaptors used in the electrical connector industry. Many old installations have imperial threads and most new fittings are metric. Thus requiring adaptors to bridge the gap.