Русско-англо-русский юридический словарь

A recommendation letter or letter of recommendation, also known as a letter of reference, reference letter or simply reference, is a document in which the writer assesses the qualities, characteristics, and capabilities of the person being recommended in terms of that individual's ability to perform a particular task or function. Letters of recommendation are typically related to employment (such a letter may also be called an employment reference or job reference), admission to institutions of higher education, or scholarship eligibility. Recommendation letters are usually specifically requested to be written about someone, and are therefore addressed to a particular requester (such as a new employer, university admissions officer, etc.), although they may also be issued to the person being recommended without specifying an addressee. (Wikipedia)

A letter of thanks or thank-you letter is a letter that is used when one person/party wishes to express appreciation to another. Personal thank-you letters are sometimes hand-written in cases in which the addressee is a friend, acquaintance or relative. Thank-you letters are also sometimes referred to as letters of gratitude. These types of thank-you letters are usually written as formal business letters. (Wikipedia)