It is usually a SMS-based app but it is not the same one for all factory-new Android phones. Some manufacturers will ship with Google Messages and some such as

It is usually a SMS-based app but it is not the same one for all factory-new Android phones. Some manufacturers will ship with Google Messages and some such as Samsung have their own messaging apps which will be the default in most but not all cases. If purchased through a carrier sometimes the default app will be the carrier's messaging app even if the phone manufacturer has their own.