Naven
Glossary
Crawl budget
How much of a site a search engine will fetch in a given period.
Proportional to a site's size and perceived importance. A small site has little, which makes wasting it expensive: duplicate URLs, infinite parameter combinations and soft 404s all consume fetches that could have discovered real pages.
A clean sitemap and an accurate lastmod are the cheapest ways to direct it.
Where Naven stands
Naven's sitemap carries a lastmod that only changes when a page actually changes, so the one signal it has for saying which page to re-fetch is not always on.