When you have a website, you need to have Google aware of it. Not only it is important Google knows about what was there last month, it is important Google knows about what you added yesterday.
To set up now the vocabulary, crawling refers to Googlebot reading the content of a webpage. Caching refers to Googlebot copying the webpage for its index.
Somewhere, in its headquarter, Google hold a cached version of all the pages it has crawled on. Well, no – Google only keeps the latest version. This is where is the tricky part. If you update pages of your website, you hope Google will crawl and cached it soon, i.e. update its index with the newest versions.
In a perfect world Google comes once a day, check all the websites and leave. In the real word Google is a busy guy. It comes once in a while, check few pages, copy them if they have changed and leave. Of course, with its tight schedule, Google wishes to save time and adapt its crawling rate to the website. Here are 3 examples of websites: news, car retailer and plumber. News are coming at least every day, a new car model might come out once a month and a new plumbing service might appear once a year. Needless to say that when you are in the case of the plumber, you still wish Google will stop by regularly to see your company is alive, things happen on your website, therefore your website is worth to display in the top 10 of the search engine result page.
To know when your page was last cached, it is very simple. Enter “cache:www.yourdomain.com/thiswebpage.html” in the address bar and you will see “… It is a snapshot of the page as it appeared on cached date…”. OMG – your site’s cached date is two months old… What should I do?, what should I do? – Google does not like me anymore… OK, take a big breath.
Did this webpage get updated during the 2 last months? If you answer NO then there is no issue at all. If a page is not cached, it does not always mean the page is not crawled. Google records the date it found changes on your page.
To really know if Google is checking on your website, you need to have a look at the crawl stats in Google Webmaster tools. Despite the fact your pages are not cached (simply because they are not changing), you might see your domain is crawled actively day after day.