Drivetrains - 3/32 vs 1/8
Most modern bike drivetrains use gears 3/32" (inch) wide, and chains to match. Some, however, use gears 1/8" wide.
As we add more speeds, the cogs get squished closer together, but they're still 3/32". That means the plates of the chain need to get thinner, because the inside gap must stay at 3/32". That's why the tolerance for error on a 10 speed chain installation is much less than that of an 8 speed.
1/8" drivetrains are usually used on BMX bikes and sometimes track bikes. Everything is a little more beefy, which makes the chainrings and cogs a little more durable. It's questionable if a 1/8" chain is stronger than a 3/32" chain, not factoring in crazy stuff like grinding a chain on a railing or something like that. It's best to just match your drivetrain (sprokets and cogs).