Metadata compatibility

Hi Guys,

Im working on a project witch will use metadatas too. It would be useful that my metadatas would be compatible with verifing metod of this site: (here is an expamle of metadatas)

I dont understand the correlation between public key, data hash and signature. What is this signature and where is comming from? I assume that signature = secret key + data hash but how is signature created? with a cardano-cli command or … ?

Thank you