A Geeky Viewpoint

A couple of sources have suggested what's the overall framework of the deal between Sony and Marvel Studios.

To start with lets go back to October; several insiders are suggesting that Marvel Studios offered in the neighborhood of $1 Billion Dollars for rights to Spider-Man.  That's B as in Boy as in Billion, cash on the barrel.  Sony turned it down. 
One Source is suggesting Marvel might have offered twice that amount had they thought Sony would sell.

In November Marvel made another offer, the details of which can be found in my post here.    Sony gave it a lot of consideration before turning it down.

So, you have turned down $1 Billion Dollars, free financing for your movies, and a gazillion other things.... 

So what is the agreement?

• Sony receives permission to use characters from Marvel Universe which they do not have rights to.   Sony has to get approval from Marvel on who they sign on for those parts or they have to use already signed actors.   IE they want to use Tony Stark, than it has to be Robert Downey Jr.    
• Sony will pay points on Gross Revenue above certain thresholds set by who they use in the films.   For example if they put an A-List actor like RDJ in a Spider-Man Film than they pay 75% of Gross Revenue above $850 Million.  (Please note I do not have the actual numbers).    While using C List Characters might only cost 25% of Gross Revenue above $850 Million.
• Marvel gets to use characters/locations/events from the Spider-Man Universe in its Movies - for FREE - but they are required to use the Same Actors that Sony Uses.  

And that is extent of the deal. 

What characters does Sony want?  
To start with Jessica Drew and/or Cindy Moon; and potentially May Parker (Peter and Mary Jane's Daughter) for the movie in the works by Lisa Joy Nolan.  
Other Characters on the wish list include Agent Coulson, Elektra, Nick Fury, Iron Fist, Tarene, Tigra, White Tiger and Nova. 
Amy Pascal has long wished to do a realistically grounded Spider-Man movie about a troubled high-schooler who has difficulty fitting in because he is a super genius.     Could you imagine Agent Coulson as a High School Principal with Spider-Man, Tarene (Thor's daughter), and Nova fighting crime.   Hum that sounds like the Ultimate Spider-Man cartoon doesn't it.  

I should note there was some discussion on whether Marvel Studios TV branch use of Kingpin was covered before the agreement.

A new actor to play Spider-Man will be signed to a joint deal in the near future.   There is a long list of potential actors, however with Spider-Man playing a pivotal role in Captain America: Civil War one can expect a new Spider-Man to be named sooner rather than later.    
The joint contract will cover two movies with a studio (Sony) option for a third.