_{I'm new to here, so I don't really know if it's a duplicate or not. Thanks for understanding}

So, I want to make decision about buying a telephoto lens, the Canon EF-S 55-250mm f/4-5.6 IS STM and Canon EF 75-300mm f/4-5.6 III USM. Which annoys me is the IS function, my friends asked me 'what are you photographing?' then I said, I would like to use the tele for outdoors and sport (with high-shutter speed of course), but within the shutter 1/20, my hands still shaky or something.

What's the difference between using an IS and not using it at all? I mean in general. Thanks

So, I want to make decision about buying a telephoto lens, the Canon EF-S 55-250mm f/4-5.6 IS STM and Canon EF 75-300mm f/4-5.6 III USM. Which annoys me is the IS function, my friends asked me "what are you photographing?" then I said, I would like to use the tele for outdoors and sport (with high-shutter speed of course), but within the shutter 1/200, my hands still shaky or something.

How much benefit will using IS give over not using it at all, in general?