# Content Freshness (/docs/start-here/freshness)



## Evergreen [#evergreen]

Evergreen lessons cover slow-changing fundamentals. Their default review target is 365 days.

## Evolving [#evolving]

Evolving lessons cover frameworks, libraries, databases, infrastructure, and engineering practices that change materially over time. Their default review target is 180 days.

## Frontier [#frontier]

Frontier lessons cover fast-moving AI, coding-agent, model, and protocol workflows. Their default review target is 90 days.

## Last verified is not last edited [#last-verified-is-not-last-edited]

`lastVerified` means a contributor intentionally reviewed the lesson for present-day correctness. A typo-only edit does not reset that date.