Wait, I'm genuinely curious how can one be Jewish and atheist? /gen
Okay so, like, Christianity is a religion, right?
Judaism is a religion and a philosophy and a system of engaging with philosophy and a culture (actually like eight cultures holding hands in a trenchcoat) and a people in diaspora. It's a religion, sure, but it's a people first. My conversion certificate doesn't say that I "converted to Judaism" but that I joined the tribes of Israel (the people, not to be confused with the temporal nation), and I usually don't refer to myself as having converted but as having been adopted, ever since I heard a rabbi object to the term "convert" and explain why.
The Four Species of the Sukkot lulav and etrog have meanings tied to how we see our community:
The lulav (a frond from a date palm) has taste but no smell, symbolizing Jews who study Torah but don't perform mitzvaot.
The hadass (myrtle branch) has a good smell but no taste, and symbolizes Jews who perform mitzvaot but don't study Torah.
The aravah is a branch from a willow tree and has neither taste nor smell, symbolizing Jews who neither study Torah nor perform mitzvaot.
The etrog, a citrus fruit somewhat like a large lemon, has both taste and smell, and thus symbolizes Jews who both study Torah and perform mitzvaot.
A lulav and etrog is not kosher unless all 4 elements are present and tied together properly and in good repair, and thus a Jewish community is not complete without all 4 kinds of Jews.
Notice, too, that there's nothing in any of that about what those people believe. Belief just... isn't that big of a deal to us. It just isn't.
Christianity is very big on orthodoxy, which is to say, correct thought. That's the whole "if you think about it, it's as bad as doing it" view on the concept of sin/bad action. You can sin by thinking things.
That's not really, like, a thing for most lines of thought in Judaism. The focus in Judaism is more on orthopraxy or right action. What you think or believe doesn't matter so much -- it's what you do, whether you show up for your community when you're needed, take care of people, be involved.
But like. You can't even draw a line between Torah study and belief in G-d -- plenty of Jews study Torah without believing in G-d, because Torah study is not about belief either. It's a community bonding exercise where you discuss and argue this week's parsha, and through that you discuss how you want to live, what kind of community you are in, and what kind of person you want to be. You can read and study Torah alone, I guess, but it's not Torah study, not really.
As with all things in Judaism, it's a 2 Jews, 3 Opinions kinda thing, and someone could (and probably will) argue with the fine points of everything I've said, but the broad points are all largely applicable to most Jews.
Or, as @dadhoc says, "Judaism is a religion of one or fewer gods."