Writing: Linking words- while, during and for

1. While is a conjunction and is followed by a clause (subject+verb). If you say: "X happened while  Y happened", it means X and Y happened at the same time.

ex: I met Peter while I was studying at the university

2. During is a preposition and it is followed by a noun. It has a similar meaning to while.

ex: I worked on a farm during my vacation

the noun after during expresses an activity that takes time. ex: during the movie/lesson/afternoon/soccer game

while and during answer the question when?

3. For is a preposition and answers the question 

How long? It is followed by a time expression. ex: I lived there for three years/six months.

ex: we´re taking a vacation for two weeks/ a couple of days.