Plinth guide: more details on versions (#7523)

Author: basetunnel

doc/docusaurus/docs/essential-concepts/versions.md

@@ -5,6 +5,12 @@ sidebar_position: 10
 # Different Notions of Version
 
 There are several different notions of version that Cardano smart contract developers must distinguish.
+For each Plutus script that is deployed on-chain, its execution behavior depends on protocol version, ledger language version and Plutus Core version (as well as the [cost model](../delve-deeper/cost-model))).
+These all influence which syntax and semantics are available for UPLC scripts.
+
+The ledger language version and Plutus Core version can be chosen by the script developer, while the protocol version is only changed by on-chain governance.
+To develop for a given ledger language in Plinth, say PlutusV3, import the `PlutusLedgerApi.V3` module from the `plutus-ledger-api` package.
+To control the Plutus Core version that Plinth targets, set the `target-version` [compiler option](../delve-deeper/plinth-compiler-options).
 
 ## Ledger Language Version
 
@@ -50,6 +56,16 @@ See [CIP-85](https://cips.cardano.org/cip/CIP-0085) for more details.
 Note that adding new builtin functions does not require a new Plutus Core version.
 Once a new builtin function is added, one can simply start using the new builtin function with an existing Plutus Core version.
 
+## Protocol Version
+The protocol version (PV) is a protocol parameter of the form `MAJOR.MINOR`, which is the main factor for determining available features and behavior of the chain.
+That behavior is implemented in the node software (which includes the Plutus Core evaluator).
+For example, starting with PV 11, the semantics of PlutusV3 + UPLC 1.1.0 is extended with [casing on constants](../delve-deeper/casing-constants).
+This feature does not affect execution of older scripts, as the UPLC interpreter takes the associated PV into account.
+
+Changes to protocol parameters are agreed upon by the decentralized governance model. A hard fork bumps the major part of the protocol version.
+For more detail, see the [Cardano Developer Portal](https://developers.cardano.org/docs/governance/cardano-governance/)
+
+
 ## Builtin Semantics Variant
 
 Depending on the protocol version or the ledger language version, or both, we may want to have different behavior of a particular builtin function.