This is a topic that usually confuses students, but it's really interesting and important to know as English Language Learners (ELL).
Have you ever heard of homographs and homophones?
You probably have.
Homographs
Also called heteronyms, their spelling is the same, that is, their pronunciation is different, e.g: tear and tear, that is to say, these words are written the same way, but they have different pronunciation, [er] and [tir], respectively. It is worth noting, in some cases, the difference occurs in the way of stressing the syllables, as in the case of object and object. As a noun, it pronounces OB-ject, we make emphasis in the first syllable and as a verb, it is pronounced ob-JECT, stressing the second syllable.
In this order of ideas, there are other concepts to learn.
Homophones
Also called heterographs. They are words that are spelled differently but they share the same pronunciation with other words, e. g: buy, bye, and by. They are pronounced /baɪ/, that is to say, they have the same sound and since they are monosyllables, stressing them is not an option. The interpretation has to come from context. Most homophones are monosyllables, which is what makes it harder to understand.
Homonyms
These are words whose spelling is the same and their sound is the same, but their meaning is different. For example:
-Bat /bæt/: A nocturnal flying mammal.
-Bat /bæt/: An instrument used to hit a ball
Another way to understand all of these concepts is by decoding the words.
The prefix homo- means "same".
The suffix -graphs means "written" or "drawn".
So, homographs are words written or drawn in the same way.
There are many homographs, homophones, and homonyms. You should google them and improve your English.