A Block Explorer allows anyone to search addresses, transactions, epochs and slots that have taken place on a blockchain. IOHK has built the Cardano Block Explorer specifically for Cardano that allows anyone to search transactions and check wallet balances. Our sister company Emurgo has also created an explorer https://seiza.com/home it's very user-friendly, see that web site for more info.
Cardano Block Explorer can be great tool if you know how to read it. Let's take for example this transaction:
On the left hand side, where you see 3 addresses, you will find the inputs. These lead into the 2 output addresses. One output address is the receiver address and the other is the “change address”, where the remaining ada from the input addresses goes back to the sender’s wallet.
As for the input, you will sometimes see multiple addresses listed. This is because your wallet is a collection of addresses (in unspent transaction outputs or UTxO) which hold ada and out of which, you can spend or send funds from. The wallet will choose inputs when you make a transaction.
Address 1: 1 ada
Address 2: 10 ada
Address 3: 100 ada
If you want to send 105 ada, your wallet would choose address 2 and 3 as inputs and send back 5 ada to your change address. That is why transactions need multiple inputs.
The values on the rightmost side correlate with amounts of the inputs.
Check out the Cardano Block Explorer for yourself.