system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Secular Humanism vs. Humanism vs. Atheism

I've been searching all throughout the Internet and I keep getting all the complex and confusing definitions when I really just want to know the main differences better all these. I consider myself an atheist (anti-religious, not non-religious) for sure, but I think I am also a humanist. However, it seems saying you're an atheistic humanist sounds redundant but then again so does the idea of secular humanism. I just want to find a clear and concise word without sounding redundant.
gpt
Atheism is simply believing gods don't exist.  It makes no statement what you should do about it.

Humanism is the belief in the betterment of mankind, as opposed to attaining some spiritual goal.  Mother Theresa, for example, as not a humanist, as she was more concerned with getting people into heaven than helping them on earth.

A secular humanists seek to better mankind to the exclusion of all spiritual and supernatural concerns.  Most humanists today are also secular humanist.