pair trading = spreader = trade difference between 2 instruments
you either expect the difference to increase , or decrease.
you can spread between two instruments (eg Italy bond BTP and Germany bond Buxl,
corn vs soya,
Nikkei Osaka vs Nikkei CME US ...)
between two calenders of a particular instrument (eg 10 years T bond Sept month vs Dec month,
soya sept month vs jun month ....),
or SPREAD THE SPREAD,
or whatever.
Is it easier to trade then outright? Yes and no depending on your expertise.
you can see some Agriculture & oil spreaders in this forum.