Matter of degree. When iron intake is inadequate for a prolonged period, iron storage in body is depleted. This is called iron deficient state. When this iron deficient state continues and iron store is further depleted, anemia develops, namely iron deficiency anemia.
Iron deficiency. Iron deficiency is the lack of iron in the body. When the level of iron is so low that hemoglobin cannot be produced, then you develop anemia: iron deficiency anemia. This is the simplified explanation.
IDA. Lack of iron usually due to too much blood loss. At your age it is most likely due to menses.
Fe deficiency anemia. Occurs when fe intake is not adequate to meet the needs of the body for red cell production. Indeed, it is not a diagnosis unto itself, but rather an indication of another problem to be discovered and corrected to avoid recurrence. Work with your doctor to address the cause of your fe deficiency state, and correct it as well as the fe deficiency state itself. Good luck.
Low Iron. In women of reproductive age, one of the most common causes of iron deficiency is heavy periods. There are other causes. Blood loss, acute or chronic, can cause it as well. To determine the cause, see a doctor for evaluation and appropriate testing and treatment.
Iron replacement. Best treatment is to replace the deficiency. This can be done with oral iron 325mg taken 3x per day with vitamin c 3x/d. If this is not tolerated then consideration can be given to using intravenous iron. However, IV iron poses greater risks than oral iron replacement- which is preferable.