1. Natality is the birth rate of a population. Due to increased natality the population density rises. 

2. Natality is a crude birth rate or specific birth rate. 

3. Crude birth rate : Number of births per 1000 population/year gives crude birth rate. Crude birth rate is helpful in calculating population size.

4. Specific birth rate : Crude birth rate is relative to a specific criterion such as age. E.g. If in a pond, there were 200 carp fish and their population rises to 800. Then, taking the current population to 1000, the birth rate becomes 800/200 = 4 offspring per carp per year. This is specific birth rate. 

5. Absolute Natality : The number of births under ideal conditions when there is no competition and the resources such as food and water are abundant, then it give absolute natality. 

6. Realized Natality : The number of births under different environmental pressures give realized natality. Absolute natality will be always more than realized natality.