a folded section placed between the leaves of another publication
"The magazine included an insert advertising our upcoming sale tucked inside the back cover."
An image inserted into text.
"I kept hitting the Insert key by accident because my finger was stuck between it and the Shift button, causing all my new letters to replace the existing text instead of appearing before them."
A key that when pressed switches between the overtype mode and the insert mode of a computer.
In plain English: An insert is an extra page or item placed inside something else, like a flyer dropped into your mailbox.
"The insertion of the key was required to turn on the alarm."
Usage: Use "insert" to refer to the physical keyboard button used to toggle between overwriting and inserting text. Do not use it to mean the act of putting something inside, which is always expressed with the verb form.
To put in between or into.
"She gently inserted a bookmark between two pages to mark her spot."
In plain English: To insert something means to put it inside another thing.
"Please insert the coin into the slot to start the game."
Usage: Use "insert" when you place an object inside something else or fit it into a gap, such as putting a coin into a slot or adding text to a document. Do not use it for general movement unless the action specifically involves placing one thing within another.
The word "insert" comes from the Latin verb inserō, which originally meant to join or bind things together. It entered English with this core sense of connecting one thing into another.