Imagine bootstrap as Market and Imagine the items we used to get in market(Bed, sofa, curtains, glasses, etc) as classes. The sofa, bed, curtains need time and effort to be made from scratch and they are made by experts. So we usually buy them to simply pick up and use it. In the same way, we use class(Bed, sofa, curtains, etc) which are made by experts by putting different codes inside it (like different woods are being cut and hammered to make bed). So that, it would be easy for us, just to pick up and use it simply as we pick up items from market.
Let’s understand bootstrap in a very very simple way. Suppose you bought one very beautiful house. You came inside it and now you need to setup the house. You need something to sit. You need something to lie on. You need something for your floor to decorate. You need something item where you can sleep comfortably. You need something items to store your books etc. You got the idea.
So, you need many things right!? And, you went in the forest and started cutting the trees. You prepared wood. Then, you started making bed, table, sofa on your own. After that, you learned to make clothes and started sewing it. You then made bed sheets, cushions, towel, curtains, etc from it. Imagine how hard it would be to do such bulky tasks!
Instead of doing such hard tasks, you just went in the supermarket and you picked up the items you liked. You picked up sofa, tables, carpets, bed sheets, curtains, living items, etc. So instead of making from scratch, you went to the supermarket and bought the items which are already made for you and you just put them in the house.
Apply same example to understand Bootstrap. Bootstrap is the market. You can use classes available in the bootstrap to create website same like you used the items in the supermarket to decorate the house.
So this is the core concept. Life is already seducing you to use the concept of bootstrap and classes & objects. HTML and CSS is one of the basic method to make website. So, if you know little knowledge about html and css too you can take the advantage of bootstrap. So, instead of making sofa, bed, and other items used in house, we go to the market to buy the things which are already made for us. In the same way, instead of doing hard coding in html and css you simply go to Bootstrap(Market) and pick up classes(Items) and use in our code to make website beautiful(House).
Wow! You just understood the concept of bootstrap. Wasn’t that easy?
So after this, if want to make website you can go to the supermarket and buy the items. Oh, Sorry! You can go to Bootstrap and pick up classes (By the you don’t need to buy classes, it’s free. XD) and use it in your code to build website. Simple as that.