Many employers in both the private and public sectors use application forms. If you are looking for a job in the charitable sector, you will also often be asked to complete an application form, and more frequently online. Having a standard format makes it easy for the recruiter to compare sprecific information given by different candidates.
If you are asked to complete an application for a job, don't send your CV, as this isn't what the employer wants. Your application will almost certainly be rejected if you do, unless the organisation has specifically agreed to accept your CV instead.