Compiled binary files can contain debug information which is not necessary for program execution, rather it is useful for debugging and finding problems or bugs in the program. Stripped binary is a binary file without these debugging symbols and thus lesser in size and gives potentially better performance than a non-stripped binary.
A stripped binary makes it hard to disassemble or reverse engineer which also in turn makes it difficult to find problems or bugs in the program.
Stripped binary can be produced with the help of the compiler itself, e.g. GNU GCC compilers' -s flag, or with a dedicated tool like strip on Unix.
References
Stripped binary Wikipedia(Text) CC BY-SA