Garden path sentences are sentences which are often misinterpreted. They are not so easy for the reader to parse. The reason is that they contain words which appear to have more than one structural analysis.
Here are five examples of garden path sentences:
The old man the boat.
The horse raced past the old barn fell.
I told the girl the cat scratched Mark would help her.
The florist sent the roses was pleased.
The government plans to increase taxes were defeated.
The first sentence can be misinterpreted because old man isn't a noun phrase. Here old is a noun and man is a verb. If we write It is the old who man the boat, the meaning is clear.
The second sentence is in passive voice. We can clarify the meaning by writing The horse which was raced past the barn fell.
In the third sentence Mark is not an object but a subject. We can rewrite the sentence as follows: I told the girl who the cat scratched that Mark would help her.
The fourth sentence is also in passive voice. We can clarify the meaning by writing The florist who the roses were sent to was pleased.
In the fifth sentence government plans isn't a noun followed by a verb. Here government plans is a noun phrase. We can clarify the meaning with a possessive noun: The government's plans to increase taxes were defeated.
Garden path sentences often confuse the reader because they have a structure which can be misread. They're called garden path sentences because to be led down the garden path means to be deceived. In many cases, the addition of a few words can help to clarify the intended meaning.