The documentation for this table can be found here https://doc.sitecore.net/sitecore_experience_platform/setting_up__maintaining/xdb/platform/reporting_database_reference
It's not totally clear from the descriptions but:
Views The total number of times the page was viewed.
Visits The number of interactions which included a view of the page.
I would presume that the interaction refers to a registered xDB interaction. See:
An interaction is the exchange of communication and commitment between
a contact and an organization that takes place through one or more
channels. The interaction registry is a service that enables you to
register or create an interaction that you have tracked in Sitecore or
in a non-Sitecore environment in the Experience Database (xDB).
So I deduce that you can record "something happening" which leads to a View being recorded. So if you're not capturing all of the possible interactions that can trigger a View - you'd expect these values to be different.
I think you're correct in your assumption for question 3 - Views is what you're after here.
Question 4 is also answered in the doc:
Value The amount of engagement value accumulated for interactions which included a view of this page.
The "LanguageId" and "SiteNameId" refer to other tables in the reporting database (check the foreign keys to see the link). Languages and SiteNames respectfully. Both have an ID and a varchar name column. Check the values you're recording in these tables and that should help answer your final question.