Rune symbol illuminated on HUD: what does this mean?

[Strummer]

In the row od three runes at the bottom of my HUD, one is illuminated. Since these are passive power-ups, I'm pretty sure I don't have to switch between them or select them, so what does this apparent "selection" mean? Many thanks.

[Salamand3r-]

I means that one is active. Some of them are only active at certain times or under certain conditions - for instance, if you have Chrono Strike it will only show active when you are airborne and it's available.

[Mysterious Pixie]

Yeah, also for example the equipment cooldown reduction rune flashes when it triggers, the air control rune is ‘on’ while you’re mid-air, etc.
Just an fyi, you can turn them off in the settings menu if they’re distracting. I only use non-chronostrike runes too so I just turned them off the increase my focus on the screen. I recommend checking the ui settings for your preferences in general too.

[Strummer]

Many thanks, gents.