Subject row locking easy question


I am studying transactions with freepascal. It is going really well now. The next thing I'd like to try is explicit locking. Can someone please describe in a sentence or two how this works- 'explicit locking doesn't happen until the record is output to servers row buffer'?  I am not sure when a record is output to servers row buffer!.

I got transactions to work today with freepascal code. Tomorrow morning I will check transactions out with data aware controls/code and then hopefully on to explicit record locking.

Thanks for any assistance-