Why did the Renaissance begin?

I have to assume that your textbook gives an answer to
this that you really ought to find.  Different scholars have different ideas and you
probably need to find the idea that your teacher will expect you to get from your
textbook.

Different people have different ideas because it
is very hard to say for sure why some idea or set of ideas got started.  Some ideas
are:

• Economic problems along with the Black
  Death led to social upheaval.  This made it so that all the old values of society were
  called into question and could be changed.


• The fall of
  the Byzantine Empire caused scholars from that empire to flee to Western Europe.  They
  brought with them classics of Greek thought that had been "lost" to
  Europe.


• Italy's social structure was changing and trade
  was bringing in new ideas.

So you see, there
are many ideas about why the Renaissance began and I think you should find the one your
teacher expects to see.