IPA = International Phonetic Alphabet

 IPA in IPA.svg
  
It's an alphabetic system of phonetic notation
based primarily on the Latin alphabet.
It was devised by the International Phonetic Association
as a standardized representation of the sounds of oral language. 
source: Wiki

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The red you see below are phonetic symbols, not letters...
I'm using them (and the video) to show you something:

The letter I is really a problem for us, Brazilian people...

Well,
/sɪt/    SIT               ≠        SEAT        /st/

ɪp/   SHIP            ≠        SHEEP      p/

/bɪtʃ/  BITCH         ≠        BEACH    /btʃ/

ɪs/   THIS*          ≠        THESE       z/  
 * in this case, there's also a S/Z difference




so,





PHONETIC SYMBOLS REFERENCES:


newenglishfile.com
oupchina.com
ipa.typeit.org