Cross- game chat on Silver member ship?

Is Cross game voice chat enabled on silver member ship? and btw what is cross game chat and cross - platform leaderboard?

you can private chat but not partys

oh and cross game chat is like a party where you can talk to people who are playing different games. cross platfrom leaderboards is for games like mw2 where its not exclusive to the PC, 360, or ps3 so they combine the ps3 leaderboards with the 360 leaderboards to show you how good you are compared to people on 2+ consoles

thanks