LiAlH4 can reduce aldehyde or carboxylic acid but it cannot reduce alcohol.
LiAlH4 during reduction removes its hydride and supply to the carbonyl carbon atom of aldehyde/Ketone or carboxylic acid.
But in alcohol, the carbon bonded to −OH cannot take this hydride. This is because the alcohol (example ethyl alcohol) act as a non-polar group to LiAlH4.