What information did the app ask of me?
It asked if it was OK to use specific information from your facebook profile in support of the Obama campaign.
Betsy Hoover, the online organizing director for Barack Obama's 2012 presidential campaign, is reported as saying
"When they clicked on the app, a screen would pop up that would say what data they're authorizing the app was giving us access to and exactly how we were going to use that data ... We built with voter history and ... other data points that Democratic campaigns use to build models. But we matched the data of your friends to that model and then reflected it back to the person who had authorized the app and said, if you want to reach out to your friends about this election on Facebook, here are the ones that you should reach out to first. And that was it...
I don't know what that "pop up" looked like but here's an example based on a 2010 IBM tutorial that might give you an idea of how it might have looked
SampleApp is requesting permission to do the following
Access my basic information
Includes name, profile picture, gender, networks, user ID, list of friends, and any other information I've shared with everyone.
I don't know the granularity of permissions that the Facebook API made available to developers but it seems reasonable that "basic information" represents the least amount of permission an app might be able to request using the Facebook API.
I should emphasise that I don't know what permissions the Targeted Sharing app requested, there are other permissions it might have requested. None of them seem to me relevant to the description's I've read of what the targeted Sharing app needed.
The 2010 IBM tutorial says
By default, applications have access to the user's public data. To access private data, applications must first request the user's permissions, which are called extended permissions. Facebook defines a large number of permissions
(my emphasis)
What did the app want me to do?
Talk to, and send messages to, your friends encouraging them to vote in the election.
According to "Inside the Cave" by Engage Research:
- OFA launched "targeted sharing" to Facebook friends who were voters in swing states
- Like Quick Donate, integration with the rest of the technology stack was key. Users received an email requesting that they contact six specific friends, with their names and photos.
- 600,000 people reached 5 million voters
- 20% of those 5 million took some action, such as registering to vote
(my emphasis)
What did I knowingly agree to, that the app will do?
You knowingly agreed to send messages to your friends. For example by clicking a "SHARE NOW" button above a list of friends.
According to "Inside the Cave" by Engage Research, it looked like this:
Remind Friends to Vote
It's more important
than ever that we
SHOW UP & VOTE
not just this year, but
EVERY YEAR
and in
EVERY ELECTION,
EVERY VOICE
must be heard and
EVERY VOTE
must be counted
Here's an easy and important way to help
president Obama win: make sure your friends in key states know when and
where to vote with our polling place lookup tool.
[SHARE NOW]
{list of friends to share message with}
It was pretty evident to the Facebook users of the Obama campaign app exactly what was happening: the users themselves were using the app to explicitly send messages to their friends.
Readers of this answer may be interested to contrast this Facebook app with, for example, the "Personality test" Facebook app by a Cambridge University researcher. Users of the "personality test" app had no knowledge that Cambridge Analytica would later improperly obtain their data with the intention to target political messages at the users' friends in support of the Trump campaign. (Note, this intention was not carried out using this data as the Trump campaign team claimed the RNC had already obtained better data they could use instead for their purposes.)