The Typical one is – to find the files with some pattern recursively in a given directory.
$ find path/to/dir -name "*.html"
You can replace the “*.html” to your own filename pattern.
Another one is, in addition to above I need the text lines inside those files starting with letter t.
$ find path/to/dir -name "*.html" -exec grep "^t" {} ;
Another version with output filename plus greped text content is
$ find path/to/dir -name "*.html" | xargs grep "^t";
-exec and xargs are the two helped commands to extend the main command functionality.