I was reading an article and it states
Tightness has returned to the London Metal Exchange (LME) aluminium spreads.
The focus point this time around is the December-January spread (CMALZ4-F5), which flared into $25 per tonne backwardation late last week.
That was acute enough to pull the full benchmark cash-to-three-months period into the widest backwardation since December 2012.
Basically, what does it mean by an aluminium spread, and what does it mean by the spreads are getting tighter? I don't really understand what backwardation means.
Also, what does "cash-to-three-months period into the widest backwardation" mean?