Card sorting and tree testing are crucial research methods in information architecture, each with a distinct purpose.

• Card sorting: It involves giving users a list of content items to group and label. This helps understand users' natural organization and naming conventions, capturing their mental models. It's great for discovering possible content groupings but not ideal for evaluating navigation hierarchies.
• Tree testing: It evaluates a navigation hierarchy by asking users to find specific items within a predefined category tree. This method requires a complete category structure beforehand and reveals whether users can effectively locate key resources, highlighting navigational issues. For example, card sorting might show that users think "FAQs" and "Support" belong together, but tree testing will indicate if users can find the "Contact Us" page within that structure.