What is the difference between an aldehyde and a ketone, and what type of molecule can they each be reduced to?

Both aldehydes and ketones have a carbonyl functional group (C=O), however in aldhydes the carbonyl carbon atom is the terminal carbon of the chain, whereas in ketones the carbonyl carbon has two alkyl groups attached to it. 

Aldehydes can be reduced to primary alcohols, but ketones are reduced to secondary alcohols.