Strategy is a nebulous term that has never been adequately defined. It’s not just planning, but it involves goals & planning.
For instance, the way I normally describe the difference is this. The goal in WWWII was to conquer Germany. But it required a strategy, which involved goals, each of which was individually planned.
Looking back, their first goal was to drive Germany & Rommel’s North Afrika Korps. out of North Africa. The 2nd goal was to cross the Mediterranean Ocean & invade Italy. The third goal was to fight their way up the boot of Italy to draw attention & support away from the Russian Army invading from the North and from the West coast of Europe where the allies planned another invasion. All of these goals required individual planing, which resulting in catching Germany in a pincer action winning the war.
Conquering Germany was the strategy, involving individual goals which were individually planned.
The accompanying article is another reasonable take on strategy.