Why is slash important abter br tag and many more?

Question

as i found the same output without using them.....

Answer 1

In HTML 5, the closing slash is optionalon void elements
img tags are Void Elements so they do not need an end tag.
Void elements area, base, br, col, command, embed, hr, img, input, keygen, link, meta, param, source, track, wbr
...
Void elements only have a start tag; end tags must not be specified for void elements.