Although you may spend a majority of your class time studying how cells divide in Meiosis and Mitosis, the cell is actually in interphase a majority of the time. The cell spends 80-90% of its time in interphase carrying out the routine functions of a normal cell.
When the cell is about to divide the preparation for this happens in interphase. The three stages of interphase are G1 (Gap 1), S (Synthesis), and G2 (Gap2).
The G1 or Gap 1 stage is where the cellular components such as organelles are duplicated. The chromosomes are not duplicated yet.
The S stage or synthesis stage is where the DNA packed into chromosomes is duplicated.
The G2 stage or Gap 2 is the stage right before cell division. The cell checks for any errors in the duplication process before continuing with cell division. If any errors are found the cell attempts to repair the duplication errors.