Aaccompanies your résumé regardless of how the two are delivered.

A cover letter is a one page formal letter that accompanies your CV or resume when applying for a job. It introduces you to an organization, draws attention and motivates the reader to invite you for an interview. 

You should consider writing an employer-centric cover letter that consist of a nice and professional introduction, body an closing.

difference where there's no picture?

answer inspecting packets in isolation from their context;