The bitcoin blockchain is public and distributed to nodes and miners around the world. It is verifiable, in that everyone can check all transactions and hashes up to the genesis block, and if an attempt is made to change, the hash values will change and the verification will fail. The bitcoin blockchain thus constitutes an immutable record of the property of bitcoins that it follows, while offering everyone the possibility of inserting other data into the blockchain. Bitcoin is not anonymous and creates a permanent record of transactions. This ultimately makes Bitcoin a terrible choice for an illegal activity in which the crime is serious enough to attract enough government effort to track the money. What Bitcoin provides is a pseudonymity: everyone can create a bitcoin address and there is no way to connect that address to someone without information from another source. So if, for example, I buy bitcoins at https://www.coinbase.com/ and send them to someone, it’s the act of buying bitcoins that gives to the police the possibility of assigning coins to me.