ETF Management Fees - When and How?

[idiotstockinvestor]

I keep reading about charges for ETFs, I did buy an ETF and noticed I payed a little extra in commission.

Does this mean I don't pay commission again or do I get dinged a certain amount each quarter, or only pay fees exactly 1 year to the date?

I've read everywhere and haven't found any details of when and how the "management fees" are taken from ETFs.

My understanding is the following:

1.) You pay extra commission/fees when buying ETFs compared to a normal stock
2.) You pay extra commission/fees when selling.
3.) You are charged management fees while holding the ETF, but it's not clear if it's charged annually, quarterly etc..

Is this an industry secret?