The command find is used to find files with various attributes.
It has many options. This makes it somewhat awkward for just
searching for a file
by name. For example, the command
find . -name "*.tex" -print
finds all the files in the current directory and any directories below
that have a name which ends in .tex and then prints the result of
the search at the terminal.
The program grep looks inside files for specified text.
For example,
grep Diophantine paper.tex
will search the file
paper.tex for any occurrences of the text ``Diophantine'' and then
then print those lines at the terminal. If you are searching in
more than one file as in grep Diophantine *.tex it will print
the name of the file in which the line was found.