A brute force program attempts every possible solution when cracking a password. These are not just useful for hacking but can be applicable in many programs. They are often inefficient and time consuming because they are so thorough.
Read more about brute force password crackers here.
In general, the lower-level programming language you use the faster performance you can expect. An exception is the Go language, which generally has speeds that parallel C++, yet in my initial testing is considerably slower in brute forcing.
The best way to measure performance is in passwords guessed per second. It's the computer's ability to generate strings and match them with the password to guess. The most powerful computers in the world can reach speeds of 1 billion passwords / second.
These programs are not optimized enough for that kind of speed, but with a fast PC you can achieve 100 million / sec running the C++ program.