Preserve means keep, maintain. For example, to "preserve the Union" would mean to keep it from falling apart into independent states.
Taphonomy
To preserve a dead body.
it means how long you live !
To keep from safety or harm
Grand Canyon Forest Preserve means," mountain lying down.
It's a jam or preserve or candied fruit
To preserve a body means to not make it rot or dry out. The ancient Egyptians were experts at this as they developed mummification; an act of preserving.
La confiture is fruit preserve, or jam.
The pickles contained salt to preserve their flavor.
Protect, preserve, or defend can all mean that.
To insulate is to add on to something to preserve an energy. For houses that energy would heat.