What is a bufferflow exploit? Is it were you load a program onto a server run it, use all availible memory and cause the server to crash?

read the tutorials.

No, what you are discribing is more a denial of service.


Programs use memory to store data.
Programs assign pieces of memory for certain data (like user input)
Sometimes Programs don't check the length of some data (for example user input) and store it in that too small reserverd space
Sometimes no bounds checking is done (it used to be to mutch overhead for the system to do it at runtime everytime), and the previous step does not cause an exception
This leaves some data in memory to be overwritten by what did not fit in the buffer.
The layout of common x86 stack often allows for the return address to be over written, allowing the attacker to alter the program flow

That is possibly the most concise description of an overflow i have ever seen , nice one