user5976: Is anything other than blocks which contain zero or more transactions, stored? Is e.g ledger state stored, is there anything special added at epoch boundaries?

user5926: Ledger state is not stored on the blockchain, but if you start with the correct initial ledger state and apply all blocks, in the correct sequence, from genesis to the current tip, you can recreate ledger state.
The things stored on the block chain include (may not be a complete list):

Blocks.
Transactions.
Stake pool registration certificates.
Stake pool parameter changes.
Stake address registrations certificates.
Staking delegation certificates (basically a special part of a transaction).
Proposals and voting for protocol parameters changes.

Things that are part of ledger state that is not stored on the blockchain (may also be incomplete):

The current UTxO state.
Current amount of ADA delegated to each stake pool.
Which stake address is currently delegated to each pool.
Rewards account balances for each stake address.
Current protocol parameters.


is there anything special added at epoch boundaries?

For the first Byron era there was an Epoch Boundary Block, but for all eras after that, there are no Epoch Boundary Blocks.

5976: <p>Is anything other than blocks which contain zero or more transactions, stored? Is e.g ledger state stored, is there anything special added at epoch boundaries?</p>
 5926: <p>Ledger state is <strong>not</strong> stored on the blockchain, but if you start with the correct initial ledger state and apply all blocks, in the correct sequence, from genesis to the current tip, you can recreate ledger state.</p>
<p>The things stored on the block chain include (may not be a complete list):</p>
<ul>
<li>Blocks.</li>
<li>Transactions.</li>
<li>Stake pool registration certificates.</li>
<li>Stake pool parameter changes.</li>
<li>Stake address registrations certificates.</li>
<li>Staking delegation certificates (basically a special part of a transaction).</li>
<li>Proposals and voting for protocol parameters changes.</li>
</ul>
<p>Things that are part of ledger state that is not stored on the blockchain (may also be incomplete):</p>
<ul>
<li>The current UTxO state.</li>
<li>Current amount of ADA delegated to each stake pool.</li>
<li>Which stake address is currently delegated to each pool.</li>
<li>Rewards account balances for each stake address.</li>
<li>Current protocol parameters.</li>
</ul>
<blockquote>
<p>is there anything special added at epoch boundaries?</p>
</blockquote>
<p>For the first Byron era there was an Epoch Boundary Block, but for all eras after that, there are no Epoch Boundary Blocks.</p>
