Katakana is sort of the more stylistic cousin of hiragana. The sounds are similar but there are two big differences in using Katakana in regard to Hiragana.

Katakana has different characters. For example the あ in hiragana is ア in katakana. Below there the standard Katakana-chart

Katakana is used only for specific words. Officially katakana is used for loanwords from other languages. For example the Japanese word for bread, パン (pan), is originally from Portugese and ビール (biru) is from the Dutch word for beer. Some more examples:

スーパー (suupaa) = Supermarket
キャンセル (kyanseru) = Cancellation
プロジェクト (purojekuto) = Project
スタイル (sutairu) = Style
カメラ (kamera) = Camera

The standard Katakana-chart looks like this

  a-column i-column u-column e-column o-column
a i u e o
ka ki ku ke ko
sa shi su se so
ta chi tsu te to
na ni nu ne no
ha hi fu he ho
ma mi mu me mo
ya   yu   yo
ra ri ru re ro
wa       o


Because the pronunciation of most katakana-words at least look like the loanwords they are derived from, it’s easy understanding their meaning. 

But that is not to say that it’s just a literal translation from English. Sometimes it can be a bit tricky reading what the katakana-word actually means because the pronunciation is a little different from the foreign words they are derived from.

For example, compare the word ‘television’ to the katakana equivalent  テレビ (terebi) or コンビニ (konbini) for a convenience store like 7-Eleven. Out of the blue you wouldn’t know what somebody was talking about right?  

Some katakana-words have even evolved into a somewhat other meaning making them even harder to understand. Take for example  アルバイト (arubaito) which means part-time job, derived from the German word arbeit.  ズボン (zubon) means trousers (or pants in American English) derived from the French word for underskirt and to make it stranger パンツ (pantsu) means shorts or underpants. Getting the two mixed will often cause laughter with Japanese natives. 

Other katakana-words are shortened or combinations of words like  テレビ and コンビニ. Other examples are: 

レジ = Cash register
フロント = Reception desk
デパート = Department store
イラスト = Illustration
メーク = Make-up


The Long Vowel

With hiragana to express a long vowel you add one. For example in the word for mother, おばあさん (obaasan) the ‘a’ coming from ba is extended by adding あ. This is important because it also changes the meaning. おばさん (obasan) without the extra ‘a’ means ‘aunt’. 

In katakana the creation of this long vowel is done by using a dash like ー. Sometimes people confuse this with the kanji-sign for ‘one’, but you can recognize it because it’s often combined with other katakana-characters. For example

You have seen

スーパー = Supermarket
ビール = Beer
デパート = Department store
メーク = Make-up

before, but other examples are

コーヒー = Coffee
バー = Bar
エレベータ = Elevator
ジュース  = Juice


Dakuten with Katakana

You probably noticed it in the examples above but just like with hiragana you can make other sounds with the standard katakana-characters by adding ” or a small dot. This is the chart for these sounds. 

  a-row i-row u-row e-row o-row
  ga gi gu ge go
  za ji zu ze zo
  da ji zu de do
  ba bi bu be bo
  pa pi pu pe po

And just like with hiragana you can make other sounds by combining katakana-characters. Look at the following chart for all kinds of combinations. 

  a-row i-row u-row e-row o-row
ky-row キャ   キュ   キョ
  kya   kyu   kyo
sh-row シャ   シュ シェ ショ
  sha   shu she sho
ch-row チャ   チュ チェ チョ
  cha   chu che cho
ny-row ニャ   ニュ   ニョ
  nya   nyu   nyo
hy-row ヒャ   ヒュ   ヒョ
  hya   hyu   hyo
my-row ミャ   ミュ   ミョ
  mya   myu   myo
ry-row リャ   リュ   リョ
  rya   ryu   ryo
gy-row ギャ   ギュ   ギョ
  gya   gyu   gyo
j-row ジャ   ジュ ジェ ジョ
  ja   ju je jo
by-row ビャ   ビュ   ビョ
  bya   byu   byo
py-row ピャ   ピュ   ピョ
  pya   pyu   pyo
w-row   ウィ   ウェ ウォ
    wi   we wo
ts-row ツァ ツィ   ツェ ツォ
  tsa tsi   tse tso
t-row   ティ      
f-row ファ フィ フュ フェ フォ
  fa fi fyu fe fo
d-row   ディ ヂュ    
    di dyu    
v-row ヴァ ヴィ ヴェ ヴォ
  va vi vu ve vo