Sorry in advance, if this sounds like a stupid question, or something basic/trivial...

I'm mainly a windows guy, programming C#, but i often do use technologies that were intended for linux machines like git, MySQL, perl scripts, memcached, php, etc...
And therefore i am exposed to these tools.

I like looking at the code base of these tools every once in a while, and something i realized in many code bases is a folder called 't' with a bunch of files with the 't' extension.
What are these files  ?
How come the folder doesn't have a more descriptive name  ?
 

I'm mainly a Windows guy, programming C#, but I often do use technologies that were intended for Linux machines like git, MySQL, perl scripts, memcached, php, etc... And therefore I am exposed to these tools.

I like looking at the code base of these tools every once in a while, and something I realized in many code bases is a folder called t with a bunch of files with the t extension.

What are these files?

How come the folder doesn't have a more descriptive name?