The invitation letter is used to explain the applicant's travel purpose, itinerary and the identity of the inviter to the visa officer so that the applicant can obtain a visa. The invitation letter is generally written by the inviter and includes the following: 1. Personal information of the inviter, such as name, address, contact information, etc.; 2. Proof of identity of the inviter, such as a copy of the passport, a copy of the ID card, etc.; 3. The relationship between the inviter and the applicant, such as relatives, friends, etc.; 4. Personal information of the applicant, such as name, date of birth, passport number, etc.; 5. Purpose of travel, such as tourism, business, visit, etc.; 6. Itinerary, including estimated time of arrival, time of departure, place of residence, etc.; 7. Financial guarantee of the inviter to the applicant, such as providing expenses and accommodation during the applicant's stay; 8. Signature and date of the inviter. Please note that visa requirements may vary from country to country, and there may be other specific requirements or format requirements. Please prepare according to the specific situation.