Schengen considers arrivals from all the other schengen countries clean, so you avoid reclearing security. There different ways this is done depending how the airport is set up, but usually means you disembark the plane straight into the departure area for flights to schengen countries

There are some other countries that schengen considers clean, such as the USA and UK, but not every airport is able to ensure passengers from those countries do not mix with arrivals from unclean for example at passport control, so reclearing security is not always consistent, even across one airport. If my flight from london arrives into Terminal 1A at Frankfurt then no need to reclear security. If it arrives into T1B then I might.

meanwhile an arrival from london into warsaw, i would need to reclear security if going for a domestic or schengen flight as I mix with 'unclean' arrivals at passport control. If i am connecting to a non schengen flight then no need to reclear security as they allow you directly into the departure area from the jetty on production of your boarding pass.

Hope this helps. If you would like more info then share the flight details