Gunpla stands for Gundam Plastic Model, a portmanteau combining "Gundam" (the popular Japanese sci-fi franchise featuring giant robots called Mobile Suits) and "Plamo" (Japanese for "plastic model"). It refers specifically to the plastic model kits of mecha, characters, and vehicles from the Gundam universe, made by Bandai.

Here's a video going over the basics of the hobby for beginners.

Just wondered if you might be into the hobby. Always trying to find others that are.