Come September, Google Chrome 53 will begin blocking Flash, such as the kind that loads "behind the scenes," as Google says, which can slow down casual web browsing. HTML5 is a lot less resource-heavy and when pages utilize it, it improves battery life, page loading and responsiveness across the web.
Following Chrome 53, in December Chrome 55 will go even further to make HTML5 the default browsing experience, excepting only sites with Flash-only support. You'll be given the option to enable Flash when you visit, so it won't change too much from the way you already browse the web. Last year, Chrome began blocking some Flash ads already, so you've likely already seen some of the effects trickling down during regular internet use if you use Chrome, after all.
What this means is you'll likely see a lot fewer hang-ups when using previously Flash-heavy sites, and fewer crashes to have to worry about -- that's the hope, anyway. It's part of a larger transition of the web to HTML5, and has been in the works for some time now.