I think you are referring to Interphase. Interphase can be divided into three smaller steps -- G1, S, and G2. Gap 1, at its simplest is the cell growing and developing. The cell is also producing some mRNA and making sure everything is available/ready to for the Synthesis (S) phase. S phase is the synthesis, duplication, of the DNA. Once that is complete, the cell enters Gap 2 (G2) which is more or less continued cell growth and production of proteins to make sure everything is set and ready for mitosis. You can think of the entire cell cycle in three broad steps. 1. Interphase and it's parts. 2. Mitosis and its four steps. 3. Cytokinesis. The entire process starts over again with the two new daughter cells, but the DNA duplication is during the S phase of interphase.