How does the Word document not delete the text you inserted after inserting the new text?

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You may have switched to "overwrite state"
Word has two types of input states: INSERT, overwrite
The default is insert state, that is, after the character is entered, the original character position is moved back
Overwrite state: The newly entered character replaces the original character at the cursor
Insert/Overwrite Toggle: Double-click the overwrite of the status bar, or press the INSERT key of the keyboard
Note: the "overwrite" of the status bar appears dimmed to "insert" and appears as black as "change with"

How does the Word document not delete the text you inserted after inserting the new text?