This is a very handy command to avoid running the same query twice. It will tell you how many total rows there are when you only need a handful. You need to run the second query immediately following the first. If you leave out SQL_CALC_FOUND_ROWS from the first query FOUND_ROWS() will simply return the number or results you got, 10 in this case.
select SQL_CALC_FOUND_ROWS field1, field2 from table where field1 = '1' limit 0,10;
select FOUND_ROWS();