Spelling, or how you write words in English is very important for several reasons. Many words sound the same but have different meanings and are written differently, such as THERE and THEIR.
Another important reason to spell words correctly is that in all the Cambridge exams, you lose marks if the words you generate are not written correctly.
On a similar subject, when to use capital letters is also important, and is different in differnt languages. For example, writing english is wrong because English always needs a capital letter, as does the word Spanish.
Some words are spelt one way in British English, and another way in American English, such as COLOUR and COLOR.
The only way to learn how to spell correctly is by using theses words often and learning by experience. There are some rules that may help, but English is not a good language for rules because there are always exceptions.
That having been said, this section will explore some rules and ideas that may be helpful.
One last thought, spelling and pronunciation are closely related. You can't spell a word correctly if you are not saying it correctly.
Finally, always check your spelling when in doubt.