FETCH FIRST and FETCH NEXT do exactly the same thing. The reason both exist because of the mandatory preceding OFFSET keyword. Using the word FIRST combined with OFFSET can be confusing to a human reader:

CopySELECT * 
FROM Foo
ORDER BY ID
OFFSET 5 ROWS
FETCH FIRST 5 ROWS ONLY; -- Does this mean rows 6 to 10, or 1 to 5?

Whereas:

CopySELECT * 
FROM Foo
ORDER BY ID
OFFSET 5 ROWS
FETCH NEXT 5 ROWS ONLY; -- Now it's clear!

SqlFiddle example here.

Similarly, you can use ROW and ROWS interchangeably, even if it breaks English grammar norms.

In SQL Server, use:

select top 10 ...

e.g.

select top 10 * from myTable
select top 10 colA, colB from myTable

In MySQL, use:

select ... order by num desc limit 10

Try with OFFSET clause

select * from products.series where state = 'xxx' order by id 
OFFSET 0 ROWS
FETCH NEXT 1 ROWS ONLY

Sometimes it's better to try things out before you ask.

SQL>     with basis as (select level l,100 - level lm from dual connect by level <=100)
  2      select l, lm from basis order by lm fetch first 5 percent rows only;

         L         LM
---------- ----------
   100          0
    99          1
    98          2
    97          3
    96          4

So the first statement works.

Second one:

SQL>     with basis as (select level l,  100 - level lm from dual connect by level <=100)
  2      select l, lm from basis order by lm fetch  5 percent rows only;

Error starting at line : 6 in command -  
    with basis as (select level l,  100 - level lm from dual connect by level <=100)
    select l, lm from basis order by lm fetch  5 percent rows only
Error at Command Line : 7 Column : 48
Error report -
SQL Error: ORA-00905: missing keyword
00905. 00000 -  "missing keyword"
*Cause:    
*Action:

So error message points out that after fetch something is missing. Or as pointed out by a_horse. Read the manual.