man find
.......
       expr1 -o expr2
              Or; expr2 is not evaluated if expr1 is true.

       expr1 -or expr2
              Same as expr1 -o expr2, but not POSIX compliant.

....

find . -type f \( -iname '*jpg' -o -iname '*mp4' -o -iname '*avi' \)

   OPERATORS
       Listed in order of decreasing precedence:

       ( expr )
              Force precedence.  Since parentheses are special to the shell, you will normally need to quote them.   Many
              of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'.

       ! expr True if expr is false.  This character will also usually need protection from interpretation by the shell.

       -not expr
              Same as ! expr, but not POSIX compliant.

       expr1 expr2
              Two  expressions  in a row are taken to be joined with an implied "and"; expr2 is not evaluated if expr1 is
              false.

       expr1 -a expr2
              Same as expr1 expr2.

       expr1 -and expr2
              Same as expr1 expr2, but not POSIX compliant.

       expr1 -o expr2
              Or; expr2 is not evaluated if expr1 is true.

       expr1 -or expr2
              Same as expr1 -o expr2, but not POSIX compliant.

       expr1 , expr2
              List; both expr1 and expr2 are always evaluated.  The value of expr1 is discarded; the value of the list is
              the  value  of  expr2. The comma operator can be useful for searching for several different types of thing,
              but traversing the filesystem hierarchy only once.  The -fprintf action can be used  to  list  the  various
              matched items into several different output files.

find . -type f -regextype posix-egrep -iregex '.*(avi|jpg|mp4)' -print