A Sender ID is a unique identifier that appears as the "sender" of an SMS when it is delivered to your recipients. It helps recipients recognize the source of the message and adds credibility to your communication. Typically, it's a name that represents your business or organization. Keep in mind that Sender IDs have character limits of 11 and may not support spaces or special characters. Choose a recognizable and trustworthy Sender ID to make your messages more effective and reliable.