For some products, you do need the Hue Bridge, but not all of them require the device as most are now equipped with Bluetooth capabilities and can be utilized via a phone with relative ease. To be sure, though, check the box for a Bluetooth symbol before making your final decision on the specific Philips Hue product you want.
Note that Bluetooth capabilities do come with some limitations though, so some may prefer to have the Bridge connectivity for smoother connections and a more streamlined process for smart home lighting.