There are many types of EMC such as Industrial EMC and

Equivalent Exchange 2.

EE2-EMC=In EE2 EMC is a source of energy on how much a dirt block or any type of tool, block, etc. is worth such as gold is worth around 2000. You need 4 gold to make a diamond which is right because diamonds are worth much more worth than gold.

IC2/1-EMC=In industrial craft 2/1 It is very simple EMC is basically Electricy/volts/current.

That means that IC2-EMC is Electricity Also EMC means Energy-Matter Currency.