Bob Kane created Batman in 1939 in the grand tradition of other pulp heroes such as 'The Shadow' and 'The Phantom'. In the sixty years since, Batman (or 'The Batman', depending on your perspective) has become a permanent landmark in popular culture and is recognizable the world over.
The concept is very simple - a young boy sees his parents murdered in a hold-up attempt, and years later avenges their deaths by stopping criminals. Regardless of all the interpretions piled on the character by the parade of writers, artists, and editors over the years, everything returns to that core concept of a desire for justice and a safe society. This likely accounts for the character's longevity over the years - the readers find their own needs and desires mirrored on the pages within.
The 'Flash' you see here is not the original Flash, of course - this one is the so-called 'silver-age' Flash. 'Silver-age', you ask? Ok, quick history lesson. Most people generally agree that the golden age of comics pretty much began in the mid-1930s, marked primarily by the first appearance of Superman in 1938. For many reasons, most of the super-hero titles that had flourished throughout most of the 1940s ceased publication by 1950. A few years later, as the science fiction genre became increasingly popular, DC Comics began to revive their old concepts. One new costume and new origin later, we have the new Flash, same as the old Flash (conceptually, that is). This revival marked the beginning of the 'silver-age' of comics.
The idea behind the Flash is even more high concept than that of Batman - the Flash runs fast. Really fast. Faster-than-the-speed-of-light fast. Before anyone starts on about how anything faster than roughly seven miles per second will achieve escape velocity and careen off the planet, I must remind you that this is fiction, ok? Just nod your head in acceptance. Thankyew.