Some employers will ask you to upload an application letter (which may also be called a covering letter) as part of your application for a specific position.
In general, an application letter provides a summary of your suitability for a specific job.
An effective application letter will clearly demonstrate why you are qualified for the job you are applying for, and explain your reasons for applying and the relevant skills you can bring to the role.
Generally, application letters will include:
The reason you are writing – which position you are applying for and where you heard about it
What particular skills and experience you can bring to the job and why you would be a good ‘fit’ for the job
A closing paragraph that thanks the employer for considering your application and indicates how you will follow up.