You wouldn't think it, but Earth orbit is a crowded and dangerous space. As with everything us humans do, no one thought about the impact of shooting all sorts of stuff into space with no way of getting it back, until it started to become a problem.
The amount of space junk flying around Earth is quite staggering. The bigger objects are actively tracked, but many smaller ones can't even be seen, until it's too late. And now, there's more of them.
A Russian rocket that failed to burn during its launch a couple of months ago has now exploded creating at least 500 more pieces of debris flying around at dangerous speeds in low Earth orbit.
Briz-M the upper stage of the Russian Proton rocket only burned for seven seconds, not the 18 minutes it was supposed to. This left it full with fuel, which has now exploded. Briz-M weighs about 22.5 tonnes without fuel.
There's no immediate danger to the ISS or satellites in orbit, but it does mean that there's something else to look out for while circling the Earth at huge speeds.