Bluetooth is a "wire replacement" technology. This means you can have a mouse without a wire (alternative approaches are available as well); headphones without wires; music players and phones without wires; portable speakers without wires. Historically, Bluetooth is not as good as a wire in terms of sound quality, but recently newer codecs (a codec converts the sound to a signal which can pass over Bluetooth) such as Sony's LDAC have emerged which are much better. Bluetooth has got absolutely nothing to do with "streaming".
A streamer plays music into your HiFi from a "file". The file may be on your laptop, a NAS or via a service such as Spotify, Amazon Music, Deezer etc.
Most high quality streamer installations don't use Bluetooth. For example, I use a streamer plugged into my DAC which gets files from my NAS via my private IP installation. There is no Bluetooth involved.
You can use Bluetooth to replace a wire in a streamer installation. Historically, this has resulted in poorer sound quality, but newer codecs exist which make it a viable approach.
