{a,b}
One word becomes two: the list in braces multiplies whatever surrounds it.
Brace expansion generates words before any other expansion: asa.{svg,png} becomes asa.svg asa.png, whether the files exist or not. It is not a glob — the disk is never consulted.
The classic portrait is the backup without repetition: cp colmeia.conf{,.bak}. The first item in the list is empty, so the expansion returns the original name and the suffixed name, side by side.
$ echo asa.{svg,png}
asa.svg asa.png
$ cp colmeia.conf{,.bak}
$ ls colmeia.conf*
colmeia.conf colmeia.conf.bak