Bootstrapping is a way for computers to get better at understanding new programs. It's like helping the computer learn how to understand a new language. It works like this:
First, someone writes a program called a "compiler". This program is able to take a new program written in the new language and turn it into a language the computer already understands, like English.
Then, they run this compiler to turn the new program into English. This gives the computer instructions on how to run the program.
Finally, they turn the English instructions back into the new language using the same compiler. This is called "bootstrapping" because the compiler is able to help itself learn the new language.