A suds saver washer, usually a top loader, will have a couple of extra buttons and an extra timer option. The following is based on the Maytag A606S, which was produced in the 60's. One button will be "Save Suds", the other will be "Drain Suds". The timer option is "Return Suds". The machine will also have two drain hoses. One is the regular drain hose, the other the suds saver hose.
When "Save Suds" is pushed, at the end of the wash portion of the cycle, the machine will divert the drained soapy water into the suds saver hose. If this is placed in a large stoppered sink or basin (20 gallon or more capacity), then the soapy water will be "saved" there for future use. The rest of the cycle will proceed normally, with rinse drains going out through the regular drain hose.
At the start of the next wash cycle, if the timer is placed on the "Return Suds" area, the washer will suck the sudsy water out of the basin instead of adding new water (although more new water may be added to make up any difference). If the "Save Suds" button is still depressed, these saved suds will be saved again for yet another re-use. If the "Drain Suds" button is pushed, then the suds will drain normally, as will the wash water for all subsequent loads.
In times when hot water and soap or detergent were much more expensive than they are today, the Suds Saver option was an economical way to conserve resources.
I think I've heard that Maytag may still offer on special order a Suds Saver washer version of one of their regular washers, but you'd have to check with your appliance dealer, or call Maytag.
There's a thread I started about the A606S or A606 that has some photos of the dual hoses, the valve that switches draining between them, and the result of Suds Return.