What is meant by the cell cycle or cell division cycle?

The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication (replication).The cell cycle consists of four distinct phases: G1 phase, S phase (synthesis), G2 phase (collectively known as interphase) and M phase (mitosis). 

G1 = growth and preparation of the chromosomes for replication; 
S = synthesis of DNA and duplication of the centrosome; 
G2 = preparation for mitosis or M phase 
M = mitosis and cytokinesis. 

Number one is sinkholes may form from water erosion