Tech companies exaggerate and outright lie to get you to buy their products. Don't believe the hype.
Your internet service provider probably claims that your connection can deliver speeds of 15 and 20 megabits per second (that's pretty fast). But that Wi-FI router you have likely claims it can transfer data at a gigabit per second (that's absurdly fast).
The fact is you'll never see gigabit speeds -- ever (not even if you're lucky enough to have Google's ultra-fast Fiber network). Most of the Internet just can't deliver you anything close to that.
So why advertise those crazy speeds? The faster your Wi-Fi router, the bigger the pipeline for all those videos, songs and games that a growing number of people are streaming on multiple devices simultaneously. That means more people can be connected at once -- even if that connection isn't as fast as you had hoped.