Struggling to make sense of HOTP for security access

Trying to wrap my head around how HOTP actually works for multi-factor authentication. The explanations online seem overly technical, and I just need a clear picture of what happens behind the scenes when a user logs in. From what I get, it involves some kind of counter, but I’m not sure how it stays secure or resets. Can anyone explain it in plain terms or point me in the right direction?