two ways to create 10 text files

The {} operator will be expanded out by the shell,

$ echo HELLO{1,2,3}
HELLO1 HELLO2 HELLO3

You can use the .. operator to expand sequences, like so:

$ echo {1..10}
1 2 3 4 5 6 7 8 9 10

If you prefix some zeroes in there, it will zerofill:

$ echo {01..10}
01 02 03 04 05 06 07 08 09 10

$ echo {01..10}.txt
01.txt 02.txt 03.txt 04.txt 05.txt 06.txt 07.txt 08.txt 09.txt 10.txt

So the command to create 10 empty text files is:

$ touch {01..10}.txt

Another way to do it is to use the seq command (which does not appear to be bundled with BSD OS's like OS X).

seq prints out numbers in a sequence.

$ seq 1 3
1
2
3

seq accepts many options. One of those is the -f flag, which will take a string to format the number according to C printf() format, like so:

$ seq -f "%02g.txt" 1 3
01.txt
02.txt
03.txt

It's fairly straightforward to pipe this output through xargs to turn it into a list of arguments for touch:

$ seq -f "%02g.txt" 1 10 | xargs touch