So, now we have the Treble Clef and the Bass Clef. We put them together and we get the Grand Staff. The Treble and Bass clefs are separated by one line (middle C) and two spaces (the B below middle C and the D above middle C).
The notes of the lines and spaces on the Treble and Bass Clefs are associated with the white keys on the piano in the above image by means of the lines drawn from the clef notes to the matching piano key. You can see that the note that connects the two clefs is a C (middle C) in between both clefs. This note is drawn as an extended ledger line above the Bass clef and below the Treble clef. We can go above and below the grand staff by means of adding more ledger lines. If we drew another line all the way across the staff it would be visually confusing. Instead we just draw a line for the note head to use where it is needed.