What are the display name, title, keyword and description?

Display name
This is the information used as a breadcrumb trail and in the left navigation. When adding the Display Name, consider how the name will affect the breadcrumb trail and navigation performance. A very long display name will cause text to wrap to multiple lines in the left navigation.

Title
This is the name that appears as the headline in your page and at the top of the Web browser window when viewing the published page. This is also the name that is recorded when someone bookmarks your page. The title plays an important role in Search Engine Optimization (SEO). The title should describe what your page is about, in just a few words. Spaces and upper case are acceptable. Avoid generic page titles such as “Welcome.”

Keyword
Keywords are also used by search engines to return accurate search request results.

Description
Descriptions are snippets of text, displayed below the links on search results pages, that provide details about the results.