The difference
Mint, lime, sugar and soda in both. The Mojito adds white rum; the Nojito leaves it out and uses more lime, so it is alcohol-free, tarter and much lower in calories.
By the numbers
Both have lime juice, mint, sugar and soda water. Only the Mojito has white rum. In parts, a Mojito is 2¼ rum, 1 lime, ¾ sugar and 3 soda; a Nojito is ¼ sugar, 1 lime and 1¼ soda. By volume, the Mojito is 44% mixer and juice, 33% spirit, 14% citrus and 9% syrup and sugar; the Nojito is 52% mixer and juice, 39% citrus and 9% syrup and sugar.
The Mojito is the stronger drink in the glass (13.1% ABV against 0.0%) and holds more alcohol (1.01 standard drinks against 0.00). The Mojito has more calories (about 136 against 35) and more sugar (8.3 g against 6.8 g). Both are built and served in a highball.