Lohari & Vasakhi both are the 'harvest festival' of Punjab.

Not necessarily. A not gate may or may not be an or gate, but an or gate must not be a not gate.

the not gate applied to and gate is nand gate

A nand gate can be made from an and gate by introducing an inverter at the output of the gate.

An OR gate is a digital logic gate.

If one or both of the inputs to the gate are "1", then the ouput of the gate will be "1" .

If both of the inputs to the gate are "0" then the output of the gate will be "0".