Mrs B's soon-to-be delivered Hyundai i20 is a "48v mild hybrid" - no electric drive capability at all, but it recovers energy braking & uses that to boost acceleration. "Real world" economy under independant tests suggest it will be similar economy to my diesel i30.
"Self charging" hybrids = bigger battery & more powerful electric motor gives limited range, limited speed electric drive capabilty.
"Plug-in" hybrid = much bigger battery & much more powerful electric motor for greater electric only range and performance.
Each step up the range of hybridisation gives a noticable step up in price. With the i20 there is no non-hybrid option & I guess that will become the norm as the end of fossil fuel only vehicles deadline gets nearer.