Cell cycle is the series of events in which cells replicate and make two new cells. Cell cycle consists of stages- $\mathrm{G}_1, \mathrm{~S}, \mathrm{G}_2$, and $\mathrm{M}$ (karyokinesis). $\mathrm{G}_1$ is the stage where the cell is preparing to divide. It then moves into the $\mathrm{S}$ phase where the cell copies all the DNA. S stands for synthesis phase (of DNA). After the DNA is copied and there's a complete extra set of all the genetic material, the cell moves into the $\mathrm{G}_2$ stage, where it organizes and condenses the genetic material, or starts to condense the genetic material, and prepares to divide. The next stage is M. M stands for mitosis. It is further divides into four stages,
Related Theory
Some cells enter $G_0$ temporarily until an external signal triggers the onset of $G_r$. Other cells that never or rarely divide, such as mature cardiac muscle and nerve cells, remain in $G_0$ permanently.
A Caution
There is a confusion in the events of Gap-1 and Gap-2 phases. [Mnemonic: $G_2$ phase two - twins - Protwins (Proteins)]