As Matt explained, it depends on what you're using your landing page for. For example, if you have a landing page that you're using for webinar signups, it's probably fine to set the metatags to "noindex, nofollow" since you're probably primarily driving traffic to the signup page via an email campaign (and not search engine results). In contrast, if you have a landing page being used to request product demos, then you'll want to set your metatags to "index, nofollow" to make sure that if someone searches for "[your company name] demo", then search engines know about your page and might return it as one of their top search results.
By default, Marketo will set your landing page meta tags to be "index, nofollow" (which means you want a search engine to crawl the page and not follow any links on the page). By default, the page title and description are blank.
Here's a
help article with more info on how to edit your landing page's meta tags.