The bases and rings used to connect a riflescope to a firearm are often the weakest link in a shooting system. Without a properly fitted connection, the very best scope and rifle combination is rendered useless. Often it is impossible to tell if you have an unsecure or ill-fitting connection until you're at the shooting bench or in the hunting field, where a poor mount or installation may show itself as inconsistent at best, and at worst cause an excess expenditure of valuable time and ammunition or a wounded animal. Think of scope mounts as the lug nuts of the shooting world.
Once installed you should never have to trouble over a loose wheel. Choosing rings and bases is not the time to pinch pennies or just make due with "good enough." The money spent will be more than made up for in reliability, ruggedness, and peace of mind. Glossary: These terms are thrown around everywhere quite loosely. Take them with a grain of salt.