What you will have applied for is an ESTA, or Electronic System for Travel Authorization.
In the past, if you wanted to enter the US under the visa waiver program, you'd just rock up in America and fill out the green I-94W form, and you didn't need to pay a fee. A few years ago, they changed the system, and now you need to apply for an ESTA before you travel to America. (Currently, ESTAs are only used for Air and Water arrivals, but they're planning to add Land Border crossings too). Originally, getting an ESTA was free, but they're recently introduced a small fee for it.
When applying for an ESTA, you supply various details. These are checked, and if you're approved then you should be fine to enter the US under the Visa Waiver Program. Various common reasons for being denied entry under the VWP are checked, so if you weren't going to be admitted then you should find out before you travel, rather than at immigration in America! In that way, it can be seen as an improvement, even with the fee...
Once issued, an ESTA is valid for the shortest of: 2 years, your passport expiring, or your passport being re-issued. You can use the ESTA website to check if your ESTA is still valid, even if you've forgotten the details, which is handy.
There shouldn't be any problem with applying for an ESTA, being approved, and not actually going to the USA for a year. All that means is that you'll need to re-apply again for a new ESTA quite soon after you trip! I know quite a few people who applied for an ESTA just before the fee was introduced, who didn't travel to the states then and there, and they haven't had any problems when they eventually came to travel.
(Having an ESTA isn't actually a visa, as it doesn't grant you the right to enter America. All it does is grant you the right to travel to America to apply for entry under the Visa Waiver Program, but they still reserve the right to not admit you. If you're turned down for the ESTA, then you'll need to travel to your nearest embassy and apply for a real visa)