Three separate functions in the run-up to the wedding — the mehndi and the sangeet in the two days before it, the haldi usually on the wedding morning — planned in one sitting and, for most families, sent on one invitation. Knowing what each one actually is decides what its block on the card has to say.
Mehndi is the henna function. The bride’s hands and feet are painted, usually by artists, over several hours. Traditionally it belongs to the bride’s side — women, cousins, closest friends, at home, an afternoon that turns into an evening with food, a dholak and everybody else getting their hands done too. Many families now hold it instead as a mixed evening at a venue, with the henna as one station among several. Both are completely normal; the invitation has to make clear which one this is, because the guest list and the dress are different.
Sangeet means music. It began as the women of both families singing traditional songs in the days before the wedding, and it is now, more often, the biggest party of the week: both families, a stage, choreographed performances, a DJ and dinner very late. When it shares an evening with the mehndi, the card says Mehndi & Sangeet and gives one start time.
Haldi is the turmeric ceremony. A paste of turmeric, oil and often gram flour or sandalwood is applied to the bride and the groom by their relatives, usually on the morning of the wedding or the day before. It is short, in daylight, and yellow. Traditionally each side holds its own at home, and the same ceremony has other names in other families — pithi in many Gujarati families, gaye holud in Bengali ones, vatna or maiyan in Punjabi ones. If your family uses one of those words, put that word on the card.
Who comes is not the same for all three. The mehndi and the haldi are the domestic ones; the sangeet is the wide one, and is often larger than the wedding dinner. So a guest invited to the sangeet and not the haldi is not being slighted — but they do have to be able to tell. The wedding itself is a separate invitation with conventions of its own: Indian wedding invitations covers the invocation, the two families’ host lines and the muhurat, and wedding invitation wording sets the register the whole set should share.