Your bicycle chain goes through a hard life, having to cope with the power going through it, moving across the cassette, and getting covered in all sorts of road grime. That is why it is important to look after your chain, ensuring it is clean and well lubed. If this is not done, they can wear themselves out, as well as other costly items like chainrings and cassettes.
A new chain can bring back the smooth gear shifting you expect from your bicycle, and if looked after can provide miles of trouble-free service. There are many different chains available, for 8 to 11 speed bicycles, with a variety of coatings designed to help prevent corrosion, and some with lightened links to reduce the overall weight of your bicycle.
It is best practice to replace the chain regularly, as otherwise cassettes and chainrings can also wear out. Regularly changing your chain will keep your maintenance costs down.