It is pronounced like 'wally'. It is an acronym for Waste Allocation Load Lifter- Earth class.
Wall E is a robot, the only of the robots that were left behind to clean up earth when it got so overrun by pollution that the humans went up in space on huge cruise ships (one being the Axiom) Over time he's become sentimental, finding "treasures" in the trash.
One day, Eve, a robot from outer space, comes and meets Wall E. WallE falls for her, and shows her all his treasures, including a plant he found. Eve's main goal is to look for plant life on earth so she immediately returns to the Axiom, with Wall E following her because of how he feels for her.
On the ship we see that humans have become hugely obese, and basically robots do everything for them. They can't even walk. Wall E and Eve get caught up in a lot of trouble - they lose the plant, find it again, the captain realizes how wonderful Earth was at one point, Eve sees WallE's feelings, the captain's Autopilot robot doesn't want to return to earth and fights the captain on the subject, Wall-E gets injured, Eve tries and fixes him but she's afraid he won't be the same.. and I won't ruin the ending.
It was a pretty good movie, it's just a little odd to watch because Eve and Wall-E don't communicate using words, just beeps and robotic sounds. Also it's almost disturbing to see the humans and earth of the future. They're fat, lazy, etc. and earth is just a giant garbage pile, where everything is owned by one company. I think the creators definately had a political agenda, but it's pretty effective.