Pruning consists of cutting certain branches of a tree to keep the tree healthy. This is usually done to the whole tree.
Trimming,, meanwhile, is the action of cutting the branches of the treetops. In certain circumstances we can do a trimming, but it is an intervention that is mostly not encouraged.
When working on your trees, it is important to call a professional who will make a complete diagnosis of your tree to be able to advise you as to the required interventions.