The chart is not an alphabet and you do not need most of it. English uses about forty-four sounds, the consonant symbols are largely the letters you already expect, and the vowel symbols are the entire remaining task.
That split is worth knowing before you start, because it tells you where the afternoon goes. Roughly fifteen consonant symbols cost you nothing at all, eight more cost you twenty minutes, and then there are the vowels, none of which can be guessed by anybody.
Eight things the alphabet buys you
- forty four sounds in English and twenty six letters, which is the whole reason a separate notation exists.
- a dictionary prints the pronunciation in this notation, so learning it turns every dictionary entry into a reliable answer rather than a guess.
- the schwa symbol, an upside down e, marking the neutral unstressed vowel that spelling never shows.
- the long and short i symbols, which is where ship and sheep become visibly different rather than a matter of opinion.
- the two th symbols, one for the voiced sound and one for the unvoiced, which English spelling refuses to distinguish.
- the ng symbol, a single character for a single sound that English writes with two letters.
- the stress mark goes before the syllable it applies to, which is the convention learners most often read backwards.
- slashes mean broad transcription, giving the sounds that distinguish words rather than every detail of a particular accent.
The symbols that look like letters and are not
A handful will catch you and they are worth meeting first. j is the sound at the start of yes, not the one at the start of jam. ŋ is the end of sing, one sound rather than two. ʃ and ʒ are the middles of ship and measure. θ and ð are the two th sounds, which are different from each other in a way the spelling never shows.
The rest of the consonants are what they look like, and the practical consequence is that a learner reading a transcription for the first time can usually get most of the consonants right by ignoring the chart entirely. That is a good thing and it is also the trap on this page.
Where it stops: the consonants feel like the job
Almost everybody learns the consonant symbols and stops. They are quick, most of them were free, and finishing them produces the feeling of having learned the chart. Then a dictionary transcription arrives, the consonants read straight off, the vowels are a row of unfamiliar shapes, and the entry is still a guess.
The stall holds because the half that was skipped is the half that was worth doing. Every consonant in bought is obvious from the spelling; the vowel is not, and the vowel is the reason you looked the word up. A learner in this state has spent the afternoon and still cannot use the instrument the afternoon was for.
Learn the vowel symbols with a keyword attached to each, one word you will not forget: the sound in ship, the sound in sheep, the sound in bed. Twelve keywords and the diphthongs, and the chart starts working.
Two transcriptions of the same word, and nobody tells you
The same word has two standard transcriptions, one British and one American, and the symbol sets are not identical. British transcription uses ɒ in lot where American does not have that vowel at all; American marks the r in bird inside the vowel symbol where British does not; and length marks appear in one tradition and often not in the other.
So a transcription is only an instruction once you know which accent it is describing, and a dictionary states its convention somewhere in the front matter that nobody reads. Decide which of the two you are aiming at, then check which one your dictionary uses, and do it once rather than being confused word by word for a year.
The free key that shows both
Wikipedia's Help:IPA/English page is the practical reference and it is better than most paid ones for this specific job. It lists every symbol English uses with example words, and it prints the British and American values side by side in the same table, so the difference above stops being invisible. Free, no account, and it is the key that most English Wikipedia articles link their own transcriptions to.
It replaced the pronunciation key printed inside the cover of a paper dictionary, which was that publisher's private respelling system, was different in the next dictionary along, and taught you nothing transferable. An American dictionary may still use a respelling rather than these symbols, which is worth checking before you conclude that a transcription is wrong.
What it looks like when it goes wrong
The recognisable failure is reading j as the sound in jam, which turns ju into a word nobody says. The quieter one is treating the length mark as the whole difference between two vowels, so ship and sheep become the same sound held for different times, and the quality difference between them is never heard.
Which of those vowel regions your own language already separates, and which it treats as one, is the question underneath all of this: the twenty that English hears and most languages do not. The consonants that actually cost you something are not the exotic symbols above: th, r, and the handful that give every learner trouble. Both sit under being understood the first time you say it.
The open question is what a transcription leaves out. It gives you a word's sounds and says nothing about which syllable carries the beat, and in English that omission is often the difference between being understood and not: which syllable to hit, and how the wrong one changes the word.