It is possible to identify two principal types of dormancy:

• Endodormancy: a period of quiescence caused by conditions or factor within the plant or organ itself. (For example the winter rest )
• Ectodormancy: ( also Ecodormancy or diapause) (exogenous or external dormancy ) a period of quiescence caused directly by adverse conditions, and lasting only while they prevail.

Dormancy affected by :

• Photo-period
• Environmental induction
• Low temperature and effective chilling temperatures in colder regions
• Hot and drought in warmer areas
• Phytohormones
• Site of the bud and bud differences
• Environment and/or cultural practices
• Dormancy breaking chemicals

Plant dormancy in temperate zones (the Winter rest) usually takes place during colder periods when plant leaves have fallen or the top growth has died down and seeds, buds bulbs or tubers exhibit a lack of growth or flowering it is a survival strategy which temperate climate species are generally believed to have to survive winters unfavourable conditions.
The plant in tropical areas  goes dormant especially during extended hot, dry periods (see dry season)

Seed dormancy is the state of inhibited germination of seeds that suspends or prevents germination even in the presence of otherwise favourable germination conditions. The breaking of seed dormancy requires moisture, sometimes cold temperatures and/or abrasion of the seed coat. ( see: scarification)

During dormancy many plants require less water, cooler temperatures and fertilizing should be withheld ( see: overwintering). Dormancy is thus a good time to transplant or prune some species of plants ( e.g. Trees).

See: Winter rest