Replace
Insert allows to insert new text into existing text, without deleting the existing text. Overwrite writes overthe existing text with the new text.For example, if my cursor was at the beginning of the word "apple", and I typed "bad", then in insert mode I would now have the text "badapple", but in overwrite mode I would have the text "badle".
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If you mean inserting columns, you can insert new columns into a worksheet, like when you may need a new column in the middle of existing ones. The Insert Function, allows you to insert new functions in a cell. The Insert key can change between Insert mode and Overtype mode, allowing you to change what happens when text is typed into existing text. In Insert mode, existing text is pushed to the right by the new text. Overtype mode replaces existing text as you type. The Insert tab on the ribbon allows you to insert lots of things, like charts or objects.
Insert
If you mean inserting columns, you can insert new columns into a worksheet, like when you may need a new column in the middle of existing ones. The Insert Function, allows you to insert new functions in a cell. The Insert key can change between Insert mode and Overtype mode, allowing you to change what happens when text is typed into existing text. In Insert mode, existing text is pushed to the right by the new text. Overtype mode replaces existing text as you type. The Insert tab on the ribbon allows you to insert lots of things, like charts or objects.
Existing text is replaced with the text being typed in the "Overwrite" mode. (As opposed to the insert mode)
If you mean typing text in the middle of some existing text, then it is Insert mode as opposed to Overwrite mode. You can also copy or cut text and then paste it into the middle of some existing text, whether you are in Insert or Overwrite mode.
Insert Mode
Existing text is replaced with the text being typed in the "Overwrite" mode. (As opposed to the insert mode)
When you are typing it will insert text by pushing any existing text over rather than replacing them which happens in overtype mode. You can turn Insert mode on by pressing the Insert key, and by pressing it again it will turn it off.
Insert - adds characters after the cursor's position. Overtype - replaces existing text with whatever the operator types.
To insert a portion of text at the top of the document, you have double click on the top and then a section called header will come up. Then you type the text in that section. This text will come at the top of every page you work on after.