Play is what kids do. They learn by playing, socialize and use up their boundless energy. Years ago, they played with sticks and rocks and anything they found lying around that could be used with imagination.
Nowadays, they play with toys. Some of the toys they play with are classics like blocks and balls and stuffed animals. Some of the toys they play with are cutting edge, electronic and so complicated that it almost takes a rocket scientist to assemble them. Ask any parent who has puzzled over directions that seem to have been translated into English by Martians and you'll get a "yes" vote on that.
But besides being complicated, the difference between how kids play today and how they played when their parents were kids is the sheer number of toys most of them have. Presents from parents, aunts, uncles, and cousins. Things they buy with their birthday money. It's really hard for parents to keep up with all the new toys that hit the shelves daily.
And this is where we come to the best way to keep your kids safe: supervision. No matter how careful you are, sooner or later kids manage to get themselves into hazardous situations. Even with toys that are guaranteed to be non-toxic American-made, like American-made play dough, for instance, kids will find a way to make them a safety hazard. If nothing else, they'll make swords out of sticks and whack their siblings with them.
Of course, you can't be with them every second, nor should you be. But checking in every few minutes is the absolute least a parent should do, especially when kids are younger and/or there are two or more playing together.
A little extra time spent making sure that they're not using safe toys in an unsafe way can allow your kid to be a kid and play, without risking permanent injury or a painful accident.