AA3675 is used on multiple routes, but the most common is between Amarillo, TX (AMA-Rick Husband Amarillo Intl.) and Dallas, TX (DFW-Dallas-Fort Worth Intl.). If on a direct flight, you'll disembark the plane in roughly 1 hour and 13 minutes. Multi-stop flights can also travel under this number, as can flights on other routes.
It's likely you'll be boarding the Embraer 175 if you're flying from Dallas, TX (DFW-Dallas-Fort Worth Intl.) to Amarillo, TX (AMA-Rick Husband Amarillo Intl.), one route used for flight number AA3675.