Quote from: TheVeteranAngel on Today at 08:28:30 PM

Blockchain technology aims to enable decentralization. But how are transactions kept secure in a decentralized system?

You see, unlike a centralized authority that is fully in charge of one's security, transactions on a decentralized system are made secure by the large number of nodes in the Bitcoin network, i.e the more the participating nodes, the higher the security. This also means that the more genuine nodes there are, the more secure our transactions become. Immutability is a practical name for it, as it describes how difficult it is for someone to rewrite, adjust or remove transaction data from the Bitcoin Blockchain. With the help of the Bitcoin consensus protocol, there will be a high resistance to change or manipulation of transactions.

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Without a central authority, how are disputes resolved on the blockchain?

This is one of the key attributes of Bitcoin that makes me like it. First, let's relate this form of disputes to the Bitcoin network in general, with the Blockchain inclusive. There are cases where someone might propose an additional update to the Bitcoin network, but it ends up being declined. This clearly shows the power of decentralization, where the Bitcoin community tends to decide what to approve and what to reject. Also you should know that before suggesting an update to the community, it must be written in a BIP form. There are so many BIPs that have been rejected, while others were accepted just to improve the Bitcoin network. It's just about who is for and who is against, something like a voting system.
You can use this link to see examples of BIPs: https://github.com/bitcoin/bips/tree/master