First of all, they are all pigmented skin spots.
A freckle is a pigmented skin spot where there are no abnormal melanocytes in the skin. It is triggered by UV radiation especially during childhood. The pigment comes from normal number of melanocytes passing more melanin to the superficial skin cells, trying (but not successfully) to protect the skin from further UV radiation.
A mole or naevus is a collection of normal melanocytes. A melanoma is a collection of melanocytes which have turned cancerous.
In general, freckles are clusters of small flat light brown marks, usually face and arms. Moles are more discrete but can vary from light brown, all the way to black. Unfortunately, melanoma can mimic a freckle or a mole. Any change of a single pigmented skin spot can be a melanoma.
Here is an example of freckles.
Here is an example of moles on the back. There are more than 10 moles just on this small section of the back.
Melanoma can mimic a light coloured freckle or any of the moles above. One needs to use high resolution examination not to miss an early melanoma. Feel free to visit our melanoma page to find out more.