What is the difference between a normal and a Poisson distribution?

This table summarizes the most important differences between normal distributions and Poisson distributions:

Characteristic Normal Poisson
Continuous or discrete Continuous Discrete
Parameter Mean (µ) and standard deviation (σ) Lambda (λ)
Shape Bell-shaped Depends on λ
Symmetry Symmetrical Asymmetrical (right-skewed). As λ increases, the asymmetry decreases.
Range −∞ to ∞ 0 to ∞

When the mean of a Poisson distribution is large (>10), it can be approximated by a normal distribution.