Sidelights have always been around, it's the first click of the light switch before the proper headlights are switched on. They are much dimmer than headlights. Intended to make the car more visible before needing to switch headlights on. Mainly useless, if it's getting a bit dark and you want to be visible, usually better to switch on the dipped headlights. Added benefit that if a headlight bulb blows, your car doesn't appear to be a motorbike, because the sidelight indicated where a headlight should be.
Daytime running lights are a totally new thing, appeared in the last few years, a bright light that is intended to be really seen in daylight, and much too bright for night use, need to be dimmed or off when headlights are switched on to avoid blinding other drivers.
Sidelights is understandable, but here I always translated "feux de position" (vive le France) to "parking lights" instead of "sidelights" (the lights are on the front & rear, not side eh).