Direct answer
Agra is best known for the Taj Mahal and Agra Fort; plan for crowds, heat in summer, and early morning visits for the Taj. Know entry/visa rules, local transport, safety, and etiquette to make your trip smooth.
Enjoy your visit: allow time to savor the Taj Mahal at different light, try local cuisine, and explore beyond the main monuments for a fuller Agra experience.