A group of people go to a island off the cost of Costa Rica to approve a theme park but they discover it has prehistoric dinosaurs  roaming around. After agreeing to a tour around the island the tech guy Dennis Nedry shuts down all the power systems then  steals dna due to him being hired to do that from a rival company, after that the main cast are attacked by a T rex and separated after escaping the T rex they are able to and turn the power system back on then regroup. Then Raptors begin to hunt down the cast but at the end they are able to escape after the T rex begins to fight and distract the raptors. Then the main cast escape the Island.  

You can learn more here about the making of the film and plot wikipedia page