When used as a verb, the French present participle expresses an action that is simultaneous with, but not necessarily related to, the action of the main verb. There are two possible uses for this in French: Modify a noun: Sachant le danger, je n'y suis pas allé.Knowing the danger, I didn't go.
Express an action that is related to the main verb. This present participle, called le gérondif, or "gerund," nearly always follows the preposition en or tout en.
It can serve three purposes: a) Describe an action that is related to and simultaneous with the action of the main verb, usually translated as "while" , “`by" or "upon": Elle lisait en mangeant. She read while eating.
b) Explain how or why something happens, usually translated by "by":
C'est en pratiquant que vous le faites bien. It's by practicing that you do it well.
c)Replace a relative clause: les étudiants venant de l'Afrique (qui viennent de l'Afrique) students who come from Africa