Simply put, phanerogams are plants that produce seeds. These are the most advanced plants on the evolutionary scale. Phanerogams used to go by the name spermatophytes. This plant classification began in 1883 when A.W. Eichler classified the entire plant kingdom into two sub-kingdoms: cryptogams and phanerogams. This traditional method of plant classification is still used by many botanists today. Phanerogams are land-based plants that are more advanced than cryptogams. Phanerogams are also easily identified by another characteristic: they are the plants that produce flowers. Source: BotanyToday.com
Interesting fact:
Phanerogams were once known as spermatophytes.