A "Thank You Letter" is a written note expressing gratitude to someone for a specific act of kindness, support, or gift. These letters can be sent for various occasions, such as after receiving a gift, attending an event, or after a job interview. They help strengthen relationships and show appreciation. Thank You Letters can be formal or informal, depending on the recipient. A formal letter might be addressed to a business associate or teacher, while an informal note could be sent to a friend or family member. Regardless of the style, the key is to convey sincere thanks.