This Sinatra application is an Employee Directory that can be used from any SMS client to find an employee's contact information. The application creates an Employee model, receives incoming SMS messages, searches for employees by name or ID, and responds with an outgoing MMS containing the employee's contact information. If no employee or multiple employees match a search query, the application returns a "Not found" message or a list of matching employees' names along with an ID number, respectively. The application uses Twilio to handle incoming SMS messages and send responses.