mysql_fetch_row is the same as mysql_fetch_array with MYSQL_NUM. That is, you get an array with a numeric index.
However, with mysql_fetch_array you can also specify MYSQL_ASSOC, in which case the array is indexed by the column names. And then there is MYSQL_BOTH where you can use either a numeric or column name index.
Using the links Matthew provide, look at how the examples differ for the two functions.