The character can comprehend and communicate with plants, including normal plants and plant creatures. The character is able to ask questions of and receive answers from plants. A regular plant’s sense of its surroundings is limited, so it won’t be able to give (or recognize) detailed descriptions of creatures or answer questions about events outside its immediate vicinity.
The spell doesn’t make plant creatures any more friendly or cooperative than normal. Furthermore, wary and cunning plant creatures are likely to be terse and evasive, while the more stupid ones may make inane comments. If the plant creature is friendly, it may do some favor or service for the character (as determined by the DM).