expand gas and allowance explanations (#1503)

* expand gas and allowance explanations

* revert unwanted autoformat change

* Update docs/build/isc/v1.0.0-rc.6/docs/explanations/invocation.md

Co-authored-by: Lucas Tortora <[email protected]>

---------

Co-authored-by: Dr-Electron <[email protected]>

docs/build/isc/v1.0.0-rc.6/docs/explanations/invocation.md

@@ -72,7 +72,9 @@ This is called _asynchronous composability_.
 ## Gas
 
 Gas expresses the "cost" of running a request in a chain. Each operation (arithmetics, write to disk, dispatch events,
-etc.) has an associated gas cost.
+etc.) has an associated gas cost. The amount of gas required for a transaction depends on the complexity of the
+operation. For example, simple transfers may require less gas, while interacting with smart contracts for actions such
+as token swaps can require more due to the higher computational work involved.
 
 For users to specify how much they're willing to pay for a request, they need to specify a `GasBudget` in the request.
 This gas budget is the "maximum operations that this request can execute" and will be charged as a fee based on the
@@ -84,10 +86,16 @@ The funds to cover the gas used will be charged directly from the user's on-chai
 
 ## Allowance
 
-Any funds sent to the chain via on-ledger requests are credited to the sender's account.
+An allowance is a feature within smart contracts that controls how much one address can spend on behalf
+of another address. Before a third party can withdraw tokens from your account, you must explicitly set an allowance for
+that third party's address, specifying the maximum amount of tokens they are allowed to transfer. This mechanism is used
+in various decentralized finance (DeFi) applications, where you might allow a smart contract to interact with your
+tokens to participate in staking, lending, or trading activities. The original token owner can adjust or revoke the
+allowance at any time, providing control over how your tokens are used by others.
 
-For contracts to use funds owned by the _caller_, the _caller_ must specify an `Allowance` in the request. Contracts can
-then claim any of the allowed funds using the sandbox `TransferAllowedFunds` function.
+Any funds sent to the chain via on-ledger requests are credited to the sender's account. If you want a contract to use
+those funds, you must specify an `Allowance` in the request. Contracts can then claim any of the allowed funds using
+the sandbox `TransferAllowedFunds` function.
 
 The Allowance property looks like the following: