Thank you cards are small cards used to express gratitude to someone for a gift, favor, or kind gesture. They often feature a simple design and a personal message, making them a thoughtful way to acknowledge someone's effort or generosity. Thank you cards can be sent for various occasions, such as birthdays, weddings, or after receiving a job interview. These cards can be purchased at stores or made at home, allowing for a personal touch. Writing a thank you card is considered good etiquette and helps strengthen relationships by showing appreciation. Many people keep a supply of thank you cards on hand for convenience.