The blockchain is a shared public ledger and transactions can be viewed by anyone.
There are a number of websites, called blockchain explorers, that visualise transactional data from the blockchain. All transactions that have ever occurred on the blockchain are publicly visible – no matter who you are or whether or not you've contributed.
Looking at transactions on a blockchain explorer allows you to discover various transactional details, such as the time a transaction took place, the volume, and the addresses involved. However, the sender's details remain private as they transact under a pseudonym called a Bitcoin address. This means that we cannot learn the individual's private information.