Front-end Framework is now widely used for its responsiveness, effectiveness and time saving purposes. As the same way, many frameworks are emerged to save your time and increase your design ideology to make better websites, or even mobile websites. Let me list in short.
I can built my website from scratch, why do I need any Front-end Framework show by you. I can do all my own. OK, then, try in 3 mins. Done. You cannot do any framing within 3 mins but you can get one of these default within 3 mins to bake your new website. Be ware, I said to bake, not to burn. LOL.
Bootstrap is one of the best Front-end framework for new developers and old developers. They have a large set of tools to use and built in support for multiple Browsers. So, write once, read any browser.
You can tweak a lot in Bootstrap in SASS mode and you can compile your own design using sass compiler. Or less compiler will work for you.
Lovely Family Host is currently using Bootstrap 4. Check it out!
Have you tried and like so much about Metro UI in windows 8 and above. I am so much liked it. They are really useful and stylish for my daily works. So, I most developed many projects with Metro UI Css. They have got bigger set of tools and one thing better than bootstrap is they included color functions. You can visit and check out any colours you like and they will set it for you. No more coding!
Materialize is based on bootstrap and used by many websites but I'm not its fun. I can tweak bootstrap and work on it. However, many people who are using android would like its style and you will get on as fast as you can. Get embed and get features. The animation is so good and You've love it in minutes. Check its manuals for more.
Front-end Frameworks are best for time saving but you have to pay for your price. You have to embed CSS and multiple js files which will not be required for your next project. They are fast and responsive, but you should think twice before using one.