The main difference between a mendicant friar and a monk.

Stability.
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Friars or mendicants professed poverty and did not possess property.  Later on the orders did own property communally.  Nevertheless, the friars were free to move about outside cloister and evangelize or teach or work in an apostolate.  Though they were assigned to different friaries or convents, they did not promise stability to a particular place.  Originally mendicants lived on alms and the generosity of the faithful. 
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Monks and hermits on the other hand are characterized by their stability in one monastery, abbey, priory, or hermitage.  The particular congregation or community usually maintains ownership of their property and are generally self-governing and self-sufficient.
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I think that's about it - if I missed anything, feel free to add to it.
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Oh!  Oh!  BTW - If you are a young man and thinking about monastic life, try entering a monastery in Europe where they make beer...  It may be more comforting than coffee during dark nights.  ;)

Of the world’s 171 Trappist monasteries seven produce beer (six in Belgium and one in The Netherlands).

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