Both a CV and an application form require a covering letter - but the format will be different for each. An application form simply needs a short statement of the post applied for and possibly an indication of availability for interview, if this is not included on the form. View this letter as a mark of courtesy. A CV requires a longer letter, which personalises your approach to an employer. A CV is a clear and concise summary of your qualifications, skills and experiences relevant to what the employer is looking for presented in an attractive way.
First impressions are very important.
Although CVs are used worldwide, CV layouts do vary across countries and some changes can make all the difference to an employer. Some require a strict chronological order and others require a definite split of education and then experience. In the UK and for international graduate programmes, it is advisable to emphasise your most relevant experiences first. This may be your education or employment depending on your own circumstances and the opportunity in question. A new graduate's CV is usually a maximum of two pages of A4 paper.