What is the Index?

Question

What is the Index and what does e.g. 5/12 mean?

Answer 1

Nonce (number generated once) is a 81-tryte hash that is output of the Proof of Work hashing once the target value has been reached. Every transaction must have a nonce for it to be accepted by the network. Source: https://learn.iota.org/faq/nonce

A typical transfer in IOTA is a bundle consisting of n transactions, these are recognized by using Index (0,1,2,3,...n)

Index 0 - Output. Recipient of the transaction and Value

Index 1 - Input. first part

Index 2 - Input. Second part

Index n - Input - Output. Balance that is sent back to sender

Source: https://domschiener.gitbooks.io/iota-guide/content/chapter1/bundles.html