From Academic Kids
In botany, flora (plural: floras or florae) has two meanings. The first meaning, or flora of an area or time period, refers to all plant life occurring in an area or time period, especially the naturally occurring or indigenous plant life. The second meaning refers to a book or other work which describes the plant species occurring in an area or time period, with the aim of allowing identification. Some classic and modern floras are listed below.
The term flora comes from Latin Flora, the goddess of flowers in Roman mythology. The corresponding term for animal life is fauna. Flora, fauna and other forms of life such as fungi are collectively referred to as biota. In relation to all the flora and fauna of a region, it is collectively referred to as biota.
Plants are grouped into floras depending on region, period, or special environment. Regions can be geographically distinct habitats like mountain vs. flatland. Floras can mean plant life of an historic era as in fossil flora. Lastly, floras may be subdivided by special environments:
- Native flora. The native and indigenous flora of an area.
- Agricultural and garden flora. The plants that are deliberately grown by humans.
- Weed flora. Traditionally this classification was applied to plants regarded as undesirable, and studied in efforts to control or eradicate them. Today the designation is less often used as a classification of plant life, since it includes three different types of plants: weedy species, invasive species (that may or may not be weedy), and native and introduced non-weedy species that are agriculturally undesirable. Many native plants previously considered weeds have been shown to be beneficial or even necessary to various ecosystems.
Bacterial life is sometimes included in a flora  (http://webster.com/cgi-bin/dictionary?va=flora)  (http://biology.usgs.gov/s+t/SNT/noframe/zy198.htm#F). Other times, the terms bacterial flora and plant flora are used separately.
Traditionally floras are books, but some are now published on CD-ROM or websites. The area that a flora covers may be either geographically or politically defined. They usually require some specialist botanic knowledge to use with any effectiveness.
A flora often contains a diagnostic key. Often these are dichotomous keys. These require the user to repeatedly examine a plant, and decide which one of two alternatives given in the flora best applies to the plant.