A more thorough explanation:

The work-product rule is a legal principle that protects an attorney's work product from being disclosed or discovered. This rule is established to safeguard an attorney's litigation strategy and is a qualified immunity, meaning it does not provide full protection from discovery.

Under the work-product rule, work-product material is subject to discovery only if the party seeking discovery can show that they have a substantial need for the materials in the preparation of their case and that obtaining the materials by other means would cause undue hardship.

For example, if an attorney creates a document outlining their strategy for a case, that document would be protected under the work-product rule. However, if the opposing party can show that they have a substantial need for that document and cannot obtain the information by other means, they may be able to obtain it through discovery.

The work-product rule is also known as work-product immunity, work-product privilege, work-product exemption, or attorney-work-product privilege.