Merge pull request #12751 from andreb0x/patch-2

updates to gas section

docs/introduction-to-smart-contracts.rst

@@ -396,14 +396,15 @@ returns that code when executed.
 Gas
 ===
 
-Upon creation, each transaction is charged with a certain amount of **gas**,
-whose purpose is to limit the amount of work that is needed to execute
-the transaction and to pay for this execution at the same time. While the EVM executes the
+Upon creation, each transaction is charged with a certain amount of **gas**.
+Imposing a cost on transactions serves to secure the network:
+it deincentivizes bad actors from spamming, and pays validators (i.e. miners and stakers)
+for the work that is required to validate new blocks. While the EVM executes the
 transaction, the gas is gradually depleted according to specific rules.
 
-The **gas price** is a value set by the creator of the transaction, who
+The **gas price** is a value set by the originator of the transaction, i.e. `tx.origin`, who
 has to pay ``gas_price * gas`` up front from the sending account.
-If some gas is left after the execution, it is refunded to the creator in the same way.
+If some gas is left after execution, it is refunded to the transaction originator.
 
 If the gas is used up at any point (i.e. it would be negative),
 an out-of-gas exception is triggered, which reverts all modifications
@@ -415,8 +416,7 @@ Storage, Memory and the Stack
 =============================
 
 The Ethereum Virtual Machine has three areas where it can store data-
-storage, memory and the stack, which are explained in the following
-paragraphs.
+storage, memory and the stack.
 
 Each account has a data area called **storage**, which is persistent between function calls
 and transactions.
@@ -505,7 +505,9 @@ Delegatecall / Callcode and Libraries
 There exists a special variant of a message call, named **delegatecall**
 which is identical to a message call apart from the fact that
 the code at the target address is executed in the context of the calling
-contract and ``msg.sender`` and ``msg.value`` do not change their values.
+contract. In practice this means ``msg.sender`` and ``msg.value`` retain
+the values that were passed to the delegator, while executing code that
+lives in the delegated contract.
 
 This means that a contract can dynamically load code from a different
 address at runtime. Storage, current address and balance still