why are files saved to ods

my files(saved forms) are saved to ODS and I can’t open them. WHY?

Hello Thomas,
ODS is an OpenDocument Spreadsheet file format that is used by some spreadsheet applications, such as OpenOffice.org Calc and Google Docs
I am not sure how this issue is connected to eM Client.
Can you please specify your issue? Are these attachments that someone sent you?