These occur where a repeated subject is deleted in a second independent clause in a compound sentence.
The compound sentence I like beer and I like wine / I like beer; I like wine is usually reduced to I like beer and wine (conjunction reduction). The repeated subject (and here verb) is deleted. This obviously only works where the two subjects of the independent clauses have the same referent. The coordinated predicate is known correspondingly as a compound predicate.
She likes beer but hates wine.
To get across to Elinor, you take the ferry or drive over the Doonan bridge.
