is this website used by hackers
Well, that really depends on your definition of a hacker.
Read this:
https://en.wikipedia.org/wiki/Hacker
If you mean the traditional definition of a hacker (see #1 in the wiki link above) - someone with deep knowledge of tech, who solve problems creatively - or a consummate programmer - then YES, several regulars here could be considered hackers. Mostly of the white-hat variety. I don't know about grey-hats, but there are plenty of grey beards here! Ha ha!
But if you mean it in the typical media definition of a hacker - a criminal who breaks/subverts security to gain unauthorised access to systems and data - AKA crackers, black-hat hackers or script-kiddies/skids. Then, no - not so much! We don't encourage, or condone illegal activity here. We're mostly about fixing problems and answering other Linux related questions.
We get plenty of wannabe skids, with zero Linux experience, who pass through and make one or two posts with questions about Kali Linux, or some other security/pen-testing distro before disappearing forever.
There are a very small number of members here who are into penetration testing/ethical hacking and know their stuff. But they aren't very active and don't post very often. Most will typically only answer questions that are above board and legitimate. There is a very fine line between ethical hacking and black-hat hacking, but as long as you keep things legitimate, it's OK to discuss them here.
So if you're interested in any aspects of Linux, or coding/scripting, security - stick around.
But if you're interested in more malicious topics - writing/distributing malware, hacking websites, stealing information, boasting about successful hacks, or dumping information - I'd strongly suggest looking elsewhere!