Some plants flower more than once in their life time. Why and How? What is the phase called?

Dear student, 
​Please find below the solution to the asked query                

Flowering depends on various factors:

• Duration of life cycle of plant
• Climatic conditions
• Growing conditions. 

Plants such as Cattleya, Iris flower more than once a year. This may happen due to the climatic factors available to these plants. Also, the plants that flower more than once a year have short life cycles. Hence, they can complete their life cycles more than once a year and so flower twice or more in a single year.
Also, flowering can be induced artificially.

Your second part is not clear. I am answering according to what I have understood
The inter flowering period represents the juvenile phase. This is because the plant though reaches maturity before flowering once, but needs to develop and gain maturity again for next round of flowering.
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Hope this information will clear your doubts about the topic.    Regards