What Records?

Many other blogs are carrying news of a new agreement between FamilySearch and Ancestry.com that will “make approximately 1 billion global historical records available online” (see: the official announcement). One billion is a lot of records. I read the announcement 3 times but I can’t figure out what records they could be talking about. Plus the time line is over 5 years. I wish they would have gone into more detail about the kind of records that will be making available.