The mandap refers to the actual physical location where the happy couple in an Indian wedding gets married. Similar to a chuppah in a Jewish wedding, or an arbor, or a pretty gazebo where you choose to center your wedding ceremony, the mandap is a decorative archway and seating area that makes for pretty pictures and creates a natural focal point for the guests at the ceremony.
More practically speaking, because a Hindu wedding involves a religious ceremony, or puja, the mandap creates an environment conducive to a puja. There are usually seats for the couple getting married and their parents, and there may be seats for other family members involved in the ceremony as well. There will also be a small table to hold the holy fire, or agni, which is required for the ceremony.
Because it’s a wedding, though, the mandap is going to be de-co-ra-ted. You’ll probably see some columns decorated with flowing fabric or lots of flowers, or both. Every couple has different preferences for their mandap, but we can assure you that, no matter their preference, it will be spectacular.