Business envelopes are envelopes which businesses use when sending items, such as printed documents in the mail. Some DL, C5 & C4 business envelopes for example are often used for mailing campaigns, to send information or for official important business purposes.
However there are other types of business envelopes which can be used to send mail such as cardboard envelopes & padded (bubble lined) envelopes which are perfect for sending more delicate items.