My space bar is deleting my typing. Why?

[benedictibe]

As I type, if I make mistake and place the cursor at the point I want to make
a correction, if I press the spacebar to push a word forward, the spacebar
instead of creating a space, deletes a letter each time it is pressed. Why?

 

[appyclappy]

Hi
You might have pressed the 'Insert' key (just above 'delete' so it's easily
done). This button switches between your typing being inserted at the cursor
and overwriting from the cursor point onwards. Press insert and see if it
helps )
Phil