A save the date is a notice stating the date of a wedding. It is typically sent to those likely to be interested or affected by the event and states the planned date of the occasion so that recipients who wish to attend know to keep that date free. Whilst some people choose to send a save the date notice, other couples might just advise friends and family verbally.
For weddings, save the dates usually take the form of a card, but can also be a refrigerator magnet, or similar item. They are generally sent out at least six to twelve months before the wedding date, and are usually followed by a formal wedding invitation.
It's not one or the other.
“It's either Save the Dates and Invitations”
or just Invitations.
Like any other invitation, it is the privilege and duty of the host to issue invitations, either by sending them herself or causing them to be sent, either by enlisting the help of relatives or friends to select the guest list and address envelopes