Conculation What is an application letter?

Get off to a direct start. In your first paragraph, explain why you are writing. Mention the job title and company name, and where you found the job listing. While you can also briefly mention why you are a strong candidate, this section should be short and to the point.
Offer something different than what's in your resume. You can make your language a bit more personal than in your resume bullet points, and you can tell a narrative about your work experience and career.
Note
Application letters typically accompany resumes, so your letter should showcase information that your resume doesn't.
Make a good case. Your first goal with this letter is to progress to the next step: an interview. Your overarching goal, of course, is to get a job offer. Use your application letter to further both causes. Offer details about your experience and background that show why you are a good candidate. How have other jobs prepared you for the position? What would you bring to the position, and to the company? Use this space to emphasize your strengths.
Close with all the important details. Include a thank you at the end of your letter. You can also share your contact information and mention how you will follow up.
How to Write an Application Letter? 
Start from the beginning, which in this case is to—
1. Create an ATS-Friendly Job Application Letter Template
You need something to write on. But instead of grabbing paper, open a text editor and adjust the format of the letter page.
No splatters guaranteed!
See how to format your job application letter:
Format of an Application Letter

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  Create enough spacing: 1–1.15 between lines, 1-inch margins, double space between paragraphs
  
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  Choose the font: Garamond, Helvetica, or Arial in 11–12 points in a font size
  
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  Align the content to the left
  
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  Pick the file format: PDF, unless the recruiter requested a Word file specifically
  
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  Name the file: JobTitle_YourName_ApplicationLetter.pdf, which in a real example would look like this, AdministrativeAssistant_OliviaRibush_ApplicationLetter.pdf
  

Disclaimer: The Applicant Tracking Software sees your application first, so if the software can’t parse it, the recruiter won’t even have a chance to read it.
By taking care of the layout, you ensure your letter of application passes the ATS scan and lands in the candidates list you’re targeting. 
Plus, with clear formatting, you’re making it easy for the recruiter to read it and quickly pick out the best bits.
That’s it in terms of your letter’s technicalities.
Let’s move on to the job letter introduction.