Crawlability refers to the ability of a search engine's crawler, also known as a spider or bot, to access, crawl, and index the pages of a website. This is an essential aspect of SEO, as it directly impacts the visibility of a website in search engine results pages (SERPs). Ensuring good crawlability involves making sure that the website's structure is easy for search engines to understand and that there are no technical issues that could prevent the crawler from accessing the content.

Crawl budget, on the other hand, refers to the number of pages on a website that a search engine will crawl within a given timeframe. The crawl budget is determined by two main factors: the crawl rate, which is the number of requests a search engine can make to a website without causing server issues, and the crawl demand, which is the number of pages on a website that the search engine wants to crawl based on factors such as the site's popularity and the frequency of content updates.

Having a good crawl budget is crucial for SEO, as it ensures that search engines are able to index the most important pages on a website, which can lead to better search engine rankings and improved SEO performance. To optimize your crawl budget, it's important to manage the number of crawled pages and prevent excessive stress on your server.