Wrong auto correction happed so frequently

I understand your frustration. Lucky for both of us, it is possible to edit, delete, add new or even turn off autocorrect. Find details here:

How to use Auto-Correction and predictive text on your iPhone, iPad, or iPod touch - Apple Support

so many words to tell OP 'don't worry your pretty little head.' lots on the problem description but whole lotta nothing on the solution :(

Generalizing Autocorrect features without providing specific examples of incorrect corrections made by an iPhone can be challenging because Autocorrect is designed to work contextually rather than solely on individual words.

Autocorrect uses machine learning and language models to analyze the context of a sentence before making corrections. This means that it doesn't just replace misspelled words with their closest dictionary matches; instead, it attempts to predict the intended meaning based on sentence structure, common phrases, and user typing patterns.

For example, if you type "I an going to the store," Autocorrect is likely to change "an" to "am" because "I an" is not a common phrase, while "I am" makes grammatical sense. Similarly, if you type "Their going to the park," it may correct "Their" to "They're" based on the sentence's context.

However, this context-aware approach can sometimes lead to incorrect corrections if the system misinterprets intent. For instance, if you frequently use slang, abbreviations, or non-standard spellings, Autocorrect may try to "fix" them in ways that don’t align with your intended meaning. Additionally, if a word is valid in multiple contexts (e.g., "its" vs. "it's"), Autocorrect may choose the wrong one based on its prediction model.

Thus, while Autocorrect is generally useful, its effectiveness depends on both the accuracy of Apple's language model and the specific way an individual types.