Update README

README.md

@@ -31,19 +31,17 @@ cryo blocks_and_transactions --rpc https://rpc.ankr.com/eth/<YOUR_API_KEY>
 --requests-per-second 30 --output-dir your_dir
 ```
 
-## Data coverage
+## Time period
 
-Latest time range:
+Blocks are between the following time range:
 
 ```
-get_time_range()
-
 | min_timestamp | max_timestamp |
 | ------------- | ------------- |
 | 2016-11-17 00:40:08 | 2025-03-25 21:17:35 |
 ```
 
-## Schema
+## Table schema
 
 - blocks/\*parquet
 ```
@@ -82,7 +80,27 @@ Schema([('block_number', UInt32),
         ('chain_id', UInt64)])
 ```
 
-## Transaction schema explained
+- The blocks and transactions tables can be joined on the
+`block_number` column
+
+## Schema explanation
+
+### Blocks
+
+```
+| Column              | Type      | Description                                                                                  |
+|---------------------|-----------|----------------------------------------------------------------------------------------------|
+| `block_hash`        | `Binary`  | 32-byte Keccak-256 hash that uniquely identifies the block.                                 |
+| `author`            | `Binary`  | 20-byte Ethereum address of the block proposer (miner).                                     |
+| `block_number`      | `UInt32`  | Height of the block in the blockchain.                                                      |
+| `gas_used`          | `UInt64`  | Total gas used by all transactions in the block.                                            |
+| `extra_data`        | `Binary`  | Optional miner-included metadata, often used for vanity tags or client identifiers.         |
+| `timestamp`         | `UInt32`  | Block's timestamp as a Unix epoch (seconds since 1970-01-01).                              |
+| `base_fee_per_gas`  | `UInt64`  | Base gas fee in wei introduced by EIP-1559 (used to compute transaction fees).              |
+| `chain_id`          | `UInt64`  | Unique identifier for the Ethereum network or sidechain (e.g., `1` for mainnet, `137` for Polygon). |
+```
+
+### Transactions
 
 ```
 | Column                         | Type      | Description                                                                 |