I'm pretty sure most of this won't make sense until you see the actual movie, but in more detail:
The movie starts off with Mr.Potato head with the alias of One eyed bob or joe or whatever, he's robbing a train for money, and like in the very beginning of the first movie, Woody comes in and releases one of his pullstring lines, like "REACH FOR THE SKY" so then Mr.Potato head calls in Ms.Potato head, One eyed betty or some stuff, and then they get away in a barbie malibu dream car driven by the 3 aliens Mr.Potato head "saved" in TS2. And to keep Woody Busy, Mr.Potato head reveals he has rigged the bridge with explosives, and pushes woody off the train. With a surprise plot twist, Jessie rides up on Bullseye and catches Woody, taking him to the Front of the the train, where he tries to stop the train, to no avail. However it turns out buzz has grabbed the middle car and pulls the train to saftey, so in pursuit of the Potatoheads, They end up catching them, and then in an original homage to the first Toy Story, Mr.Potato Head brings out Slinks, aka THE ATTACK DOG WITH THE BUILD IN FORCE FIELD, and then Slinks grabs his tail and forms an actual force field, then Woody brings out Rex, also known as THE DINOSAUR THAT EATS FORCE FIELD DOGS, but it doesn't work, and then Ham, the evil Doctor Porkchop beams the potatoes and their dog up into this gigantic battleship he has, and presses a big button that says DEATH BY MONKEY, which I think is from Toy story 2, and release a barrel of monkeys that fall to the ground and then flood the entire canyon where the story is taking place, and starts to tie or rather hold down the entire Sheriff Woody gang and buzz lightyear. At this point this story ends, and we revert back to Andy, who is still 5 or 6 years old, playing with his toys. And it turns out his mom has been filming them this entire time. A few more home videos flash, and we get to the original story. Where Andy is going to college and his Toys sit unused in a box. At this point, they have found phones bought to them by the Army men. The have a plan to make one phone ring and get Andy to open the box, in hopes Andy will play with them again. But the plan fails.
I am too obese to explain the rest of the movie to you and I shall now go to slumber. Okay, bye.
TL;DR: mondaysmondaysmondays