As is customary, the title of the first post of this blog is "Bonjour, le monde", the best french translation I found of "Hello, world" :p
To learn more, I googled about the origin of this famous message.
This takes us back to 1970 when Brian Kernighan describes the first compiled computer program displaying "hello, world "(without capital letters and with a comma), as an example of BPCL, a programming language created in 1966 at the origin of B, ancestor of the better known C language..
Today, "hello, world" (that became over time "Hello World!") are the words traditionally written by a computer program whose purpose is to make a quick demonstration and/or indicate that it was correctly installed. In the case of a blog (and this one in particular), it's often the first post telling the user that its site is working.
TL;DR: We can summarize as follows: if your computer says "hello, world", that means that everything is fine (at least so far).