Fewer and Less
Fewer means "not as many" and is used for countable nouns. There are fewer trees in the park these days. Fewer people smoke cigarettes. Fewer VCRs are being sold.
Less means "not as much" and is used for non-countable nouns. The river has less water in the fall. We play less music on week nights. It will be less work if you let the dishes soak before you wash them.