In very short Data Governance encompasses.
Discovery: Identifying all data assets, like finding items in a house.
Classification: Categorizing data, akin to sorting items (heirlooms, photos, etc.).
Policies and Rules: Setting guidelines and enforcing rules for data handling, similar to deciding what to keep, donate, or discard.
Metadata: Describing data for easier use, like labeling bins.
Monetization: Using well-governed data for financial gain, compared to selling valuable items found during cleaning.
Each pointer having its own detailed process, but if followed throughly we could effectively have high data maturity.