clarification on how recuva works

does recuva mark deleted files as not-deleted, or does it read the deleted file and write it elsewhere?

in other words, let's say i restore a 1gb file. does this mark that space in particular as no longer deleted, or could it possibly write over other deleted files / empty space?

Recuva writes a new file on whatever device and in whatever folder you choose. It does not alter the deleted file, which can be recovered again if you so wish. The deleted file is already marked as free space, so if you attempt to recover it to the same device (i.e. write a new file on the same device) it may overwrite the deleted file that's being recovered, with undesirable results. Also the deleted file can at any time be overwritten with any new file, making recovery impossible.