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As far as I understand it, if you churn, you basically send all your money to yourself but mostly in little chunks which resemble "normal" transactions. As Monero adds decoys for all transactions, each of these transactions lowers the probability for a chain analysis company to associate your coins to a single account.
This seems to be useful above all if you withdraw coins from an (CEX) exchange, make a transaction to "anonymize" it, and deposit some of the coins to another exchange (which may use the same chain analysis company's services). In this case, the probability the CEXes may associate to your coins belonging to the same wallet/owner lowers quite significantly.
Now the privacy risk seems to be that if you exaggerate it may become obvious that you're churning:
I would love more opinions on that and a comment if I've understood the technique correctly
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Exactly! You're on the right track. You should read this everything is detailed on this page:
https://github.com/antichainalysis/xmr-churner/blob/main/writeup.md