Are there different generations of bricks?

Hi. Complete LEGO noob here. I recently bought a large tub of random assorted bricks at a flea market to use for a project at work, and noticed there are some differences in the bricks. Now, I know nothing about LEGO other than that I occasionally treat myself to a set to build over the winter with my wife, and so i have no idea about the collectible/enthusiast side of it. Are there different generations of bricks? Are they from different factories? submitted by /u/GooneyBird87 ...