Transaction types
You can interact with the Ethereum JSON-RPC API using different transaction types (specified by the type parameter).
The following methods use a unique format depending on the transaction type:

Legacy transactions

Transactions with type 0x0 are legacy transactions that use the transaction format existing before typed transactions were introduced in EIP-2718. They contain the parameters nonce, gasPrice, gasLimit, to, value, data, v, r, and s. Legacy transactions don’t use access lists or incorporate EIP-1559 fee market changes.

Access list transactions

Transactions with type 0x1 are transactions introduced in EIP-2930. They contain, along with the legacy parameters, an accessList parameter, which specifies an array of addresses and storage keys that the transaction plans to access (an access list). Access list transactions must specify an access list, and they don’t incorporate EIP-1559 fee market changes.

EIP-1559 transactions

Transactions with type 0x2 are transactions introduced in EIP-1559, included in Ethereum's London fork. EIP-1559 addresses the network congestion and overpricing of transaction fees caused by the historical fee market, in which users send transactions specifying a gas price bid using the gasPrice parameter, and miners choose transactions with the highest bids.
EIP-1559 transactions don’t specify gasPrice, and instead use an in-protocol, dynamically changing base fee per gas. At each block, the base fee per gas is adjusted to address network congestion as measured by a gas target.
EIP-1559 transactions contain, along with the accessList parameter and legacy parameters except for gasPrice, a maxPriorityFeePerGas parameter, which specifies the maximum fee the sender is willing to pay per gas above the base fee (the maximum priority fee per gas), and a maxFeePerGas parameter, which specifies the maximum total fee (base fee + priority fee) the sender is willing to pay per gas.
An EIP-1559 transaction always pays the base fee of the block it’s included in, and it pays a priority fee as priced by maxPriorityFeePerGas or, if the base fee per gas + maxPriorityFeePerGas exceeds maxFeePerGas, it pays a priority fee as priced by maxFeePerGas minus the base fee per gas. The base fee is burned, and the priority fee is paid to the miner that included the transaction. A transaction’s priority fee per gas incentivizes miners to include the transaction over other transactions with lower priority fees per gas.
Read the ConsenSys EIP-1559 primer for more information on how EIP-1559 changes Ethereum.