What problems is Casper / highway solving?
Lots of progress in designing efficient.
In Classical models finality is binary. Problem because nodes have wrong incentives. Out of many blocks, only 1 is the final one.
In highway model is expressed by fraction of nodes needed to break protocol rules for a block to be reverted.
Nodes can configure their security thresholds, allowing those with lower threshold to reach finality faster than the ones requiring higher levels of confidence.