How do you guys know what the temperature is? My laptop doesn't do that.
It's not a laptop-specific feature or anything. Every processor, both CPUs and GPUs, come with temperature monitors on-board inside them.
You can use tools such as RealTempGT to monitor both. Some programs, such as EVGA's Precision and MSI's Afterburner, will display GPU temperatures in-game in an overlay, similar to FRAPS' FPS counter.