Naivedhya (Sanskrit: नैवेद्य) a Sanskrit word meaning 'offering to God' in the stricter sense of the words. It could be any offering, tangible or intangible. A resolution, a promise or even a willingness to do, perform or restrict certain things can also connote an offering to God.
Offering of food items forms part of the 'Upacharas' or Services/Offerings offered to a deity who has had the Prana Prathistha ritual performed to it. Therefore the murthi or vigraha is revered as a living entity who is offered food, fruits, and betelnut among others. Temples usually have stricter worship routines that include offering upacharas like naivedhyam multiple times a day as in Thirumala Venkateshwara Temple, Jagannatha Temple, the 6 main abodes of Lord Muruga, and many Hindu temples all over the world. Most temples will allow only trained pujaris to cook the naivedhyam. Food offered directly to the deity is considered as 'Maha Prasada' (Great Offering) and it is considered extremely aupicious to be able to partake a morsel of that. Offerings of food in home shrines are relatively simpler though the Hindu having observed cleanliness of body and mind will attempt to do so using sattvik items and in a purified space. A common practice is to mix the offered naivedhyam back into the remaining food before partaking it.
Naivedyam means food offered to a Hindu deity as part of a worship ritual, before eating it. As such, tasting during preparation or eating the food before offering it to God is forbidden. The food is placed before a deity and prayers are offered. Then the food is consumed as a holy offering. The offerings may include cooked food, sugarcane, or fruits. Vegetarian food is usually offered and later distributed to the devotees who are present in the temple. Non-vegetarian is prohibited in most of the temples, but there is evidence for non-vegetarian food – offerings to Goddess Kali include animals such as goats or roosters, which are slaughtered in the temple precincts and offered. Many Hindus offer cooked food or some fruits to a picture or idol of a deity before they eat it.
However, one needs to differentiate Naivedhya from 'Prasad'. Prasad is what one gets from the God. The meaning of these words is usually attributed to food offered to and receive from the house of Gods in the form of eatables.