The white card [白札 - しろふだ, shirofuda] included in many decks has a few uses:
Many decks, though not all, include an extra card outside of the wrapper. This is called a “sample” [見本 - みほん, mihon] card, and its purpose is to display the quality of the deck within the wrapper. It is not traditionally intended for play, and may sometimes be marked with a cut corner to distinguish it as such.
This sample card may take the form of any card in the deck, but is very frequently a copy of the Cherry Blossom Ribbon with “見本” in place of the usual “みよしの” miyoshino.
In a pinch, a sample card in good condition may be used to fill the role of a joker or the white card for gameplay.
For the standard Hachihachibana design, the Pine and Plum Blossom cards read あかよろし akayoroshi, which is one of many names for the yaku consisting of the three Poetry Ribbons that appears in many games. The literal translation is akin to “Red is good.”
The Cherry Blossom card instead reads みよしの miyoshino in reference to Mt. Yoshino in the Nara Prefecture of Japan, which is renowned for its bountiful Cherry Blossom trees.
Those are the standard inscriptions, but note that some (especially older) decks use different text for the Ribbons, and may not limit the text to the three cards we now think of as Poetry Ribbons! For instance, decks made by Tanaka Gyokusuido feature an alternate name for the aforementioned yaku on each of the three relevant cards - うらす urasu, よろし yoroshi, and すがわら sugawara - and also have the name of another yaku, たてさん tatesan on the Wisteria, Iris, and Bush Clover Ribbons.
Nintendo currently has three major brands of standard hanafuda cards, though historically they have sold many many more. These brands all feature the same artwork, but may be considered to be of differing levels of “quality”. The biggest differences seem to be in the weight of the cards and the protective coating that is applied to them. From “best” to “worst”, these are:
Nintendo also makes various Character Hanafuda decks whose cards are decorated with characters from, for example, the Mario or Kirby franchise.
Unfortunately there is no centralized location to find a given deck you might want; however, see Places to Buy Hanafuda for some starting points.
These are two different kinds of Japanese playing cards, similar in size and shape, but much different with regards to actual card design and deck configuration. Whereas hanafuda consist of 12 suits of 4 cards each, and are decorated with somewhat abstracted images of East Asian flowers, kabufuda consist of 4 copies each of values 1 to 10, mostly represented by black stripes (abstracted from the Western suit of clubs).
It is important to note that the two decks are not interchangeable in terms of what games they can be used to play; kabufuda games can be adapted to play using hanafuda by assigning each suit a numerical value (see here), but kabufuda cannot generally be used to play hanafuda games because of the differing deck structures.
Note as well that hanafuda and kabufuda come in very similar packaging, often with the exact same brands and images; for example, Nintendo sells daitōryō brands of both these decks, with identical packaging with the exception of the addition of the kanji “株札” [かぶふだ, kabufuda] or even just “株” [かぶ,kabu] on the bottom right of the kabufuda box.
There are two ways to look at this. First, the word “hwatu” can be taken to mean “Korean hanafuda.” From this point of view, any flower cards made in Korea, and intended for consumption in Korea, are hwatu, regardless of the art style or construction of the cards.
On the other hand, one might consider the word to refer to a particular style and construction of flower card deck, which is the most common realization of the former definition of “hwatu.” These cards are made of thick (usually, but not always red) plastic, with a checkered texture on the back and a smooth front. The artwork on the cards differs slightly in style from their Japanese counterparts. Notably, the five Bright cards each feature a circled 光 [ひかり, hikari, “light”] symbol, which may be useful to beginners for distinguishing betwen those and the Animal cards. Furthermore, these decks often include between one and six “joker” or extra cards, which differ in design among manufacturers.
The hwatu described in the previous paragraph may be considered a good choice for beginners because of the marked Brights, as well as their being less delicate than the paper-made hanafuda. The extra cards may also be useful for playing the popular Korean game Go-Stop, which regularly makes use of them. Aside from these factors, the games playable with hwatu and hanafuda are the same, regardless of how you define “hwatu,” so beginners need not fret over the choice of one over the other.
In no particular order, some considerations when buying a deck, and especially your first deck, are as follows.
There are probably two really good answers for this question:
Hanafuda make up an “open system” so to speak; that is, the cards can be used to play a practically infinite number of games, just like Western playing cards. For a non-exhaustive list of hanafuda games, see Hanafuda Games.