The Foire de Paris is a commercial fair that has been held in Paris every year since 1904. It takes place during the last week of April and the first half of May, which means that hotel prices go way up during these weeks, at least in the southern half of Paris.
At the fair in 2013 there were 1,829 exhibitors divided into three main groups: the home, cultures of the world and well-being/leisure.

Entrance to Paris Expo

Warning! Sale of phony tickets!
Even though I am a notorious non-consumer, I decided to go and see what all the fuss was about. Before leaving home, I booked a ticket online to avoid queuing to get one. The ticket cost twelve Euros and was valid for one admission on any day of the fair.
(For the 2019 fair, an online ticket cost only € 11.00 if bought in advance, or € 12.50 if bought online while the fair was in progress. But a ticket bought at the gate cost € 15.00, in addition to the time lost by standing in line.)

Hall 4

Visitors map of the Paris Fair, 2013
As in any big fair (like the Frankfurt Book Fair, which I attended for thirty-four consecutive years), there are so many exhibits that no one person can hope to see them all. So you just wander around and take pot-luck, or if you are better organized than I am you can study the maps and find the locations of the exhibits that interest you.
Out of the eight exhibition halls at “Paris Expo”, the Paris fairgrounds at Porte de Versailles, six were in use for the fair in April and May 2013.

Halls 3 and 4
Over two hundred shows, conferences and events are held at Paris Expo each year, with about six million visitors. Paris Expo claimed (when I was there) to be the fourth largest venue for trade fairs in Europe. The largest was said to be the Köln Messe in Cologne, Germany, followed by Geneva Palexpo in Geneva, Switzerland and the Expocentre Fairgrounds in Moscow, Russia. (This list changes from year to year, however, as they all keep building more and larger exhibition halls.)
My photos in this post are from 2013. I revised the text in 2019.
See more posts on the 15th arrondissement of Paris.
I go to a lot of foires or fairs but in the gastronomy/wine area lol!!
I’ve been to Medica in Dusseldorf – 16 halls of medical stuff. It took me a day to go round two of them!
We were there all of May this year (2019) and it might have been fun although, like you, I am a major non-consumer. I’m always up for an adventure though and this looks like one. Fun.