There are 4 stages/phases in a menstrual cycle:
Menstrual phase - It begins when someone gets their period. It happens due to lack of fertilization of the egg released in the ovulation phase. The thickened lining of the uterus to support a pregnancy is no longer needed and is shed through the vagina.
Follicular phase - It also begins when someone gets their period so there is some overlap between the first two phases. In this phase, follicle-stimulating hormones are released which stimulates the ovaries to produce follicles that contain immature eggs. The healthiest egg(s) will mature and the remaining will be re-absorbed into the body.
Ovulation phase - The phase when the ovary releases the mature egg(s) which travels down the fallopian tube to be fertilized by the sperm. After a day, the egg will die or dissolve if it isn’t fertilized.
Luteal phase - In this phase, the body prepares for pregnancy. If pregnancy does not happen , the body might display Pre-Menstrual Symptoms (PMS)