search within files

Any ideas for a program (free preferred) that will allow me to search for a word or specific phrase within a file (or set of files)?

I'm not referring to the typical windows-type search that will list folder names or filenames for me to open manually to view the contents, but rather, will allow me to search the contents of file(s) without actually opening the file(s). Thus, narrowing down the number of folders/files to open manually.

I hope my question is clear to anyone reading this. If not, please let me know and I'll try to rephrase my question.

Thanks for your help.

Happy Holidays to all!