Syntax of brace expansion

Example of brace expansion taken from ion online manual

echo filename.{ext1,ext2}
echo job_{01,02}.{ext1,ext2}
echo job_{01_{out,err},02_{out,err}}.txt
echo {1..10}
echo {10..1}
echo {1...10}
echo {10...1}
echo {a..d}
echo {d..a}
echo {a...d}
echo {d...a}