What you are looking at right now are 350 of the most leaked passwords on the Have I Been Pwned database. The visualization tool shows how much time it takes to guarantee bruteforce attack on each password depending on the attacker's hardware (the average time is half of the guaranteed time). Consider that, in real life, attackers use much more sophisticated methods to attack passwords, so if your password is on the compiled list, you should be really worried, and change it immediately. As for what each X axis mark means, 1 GPU represents a high-end graphics card that can try about 100.000.000.000 password combinations per second. 25 GPUs represents a cluster of 25 high-end graphics cards that can try about 500.000.000.000 password combinations per second. Finally, NSA represents the (not confirmed) theoretical estimated computational power of agencies like the NSA, which can crunch about 1.000.000.000.000 password combinations per second. And just to put a bit of context, 10,000 seconds are equivalent to less than 3 hours, 1,000,000 seconds are equivalent to 12.5 days, 1,000,000,000 seconds are equivalent to more than 31 years and 30,000,000,000 seconds are equivalent to 9.5 centuries.