The type of chain you need will depend on the type of bike you are riding. A number of different chain widths are available, to suit specific bike types such as BMX, or to fit different road and MTB drivetrains (e.g. an 11-speed cassette requires a different chain to a 9-speed one – the chain must be thinner in order to fit into the narrower spaces between the sprockets.
Whatever bike you ride, chain maintenance is key. Chains will wear and stretch over time, and a worn chain will damage the teeth on your chainrings or sprocket. It’s important to keep your chain clean and lubricated to minimise wear, and to regularly check chain length so it can be replaced when necessary.