From the link in the OP
"A walker or walking frame is a tool for disabled or frail people, who need additional support to maintain balance or stability while walking, most commonly due to age-related physical restrictions. In the United Kingdom, a common equivalent term for a walker is Zimmer frame, a genericised trademark from Zimmer Biomet, a major manufacturer of such devices and joint replacement parts."
"The basic design consists of a lightweight frame that is about waist high, approximately 12 inches (30 cm) deep and slightly wider than the user. [...] The front two legs of the walker may or may not have wheels attached, depending on the strength and abilities of the person using it."
"Traditionally, a walker is picked up and placed a short distance ahead of the user. The user then walks to it and repeats the process. With the use of wheels and glides, the user may push the walker ahead as opposed to picking it up. This makes for easier use of the walker, as it does not require the user to use their arms to lift the walker. This is beneficial for those with little arm strength."
"A different approach to the walker is the rollator, also called wheeled walker, invented by the Swede Aina Wifalk in 1978, herself a polio sufferer. Although originally a brand name, "rollator" has become a genericized trademark for wheeled walkers in many countries, and is also the most common type of walker in several European countries.
The rollator consists of a frame with three or four large wheels, handlebars and a built-in seat, which allows the user to stop and rest when needed. Rollators are also often equipped with a shopping basket. Rollators are typically more sophisticated than conventional walkers with wheels."
And again, from a US source:
What’s the Difference Between a Walker and a Rollator?
The main difference between a walker and a rollator is that a walker is a frame with handles and legs that needs to be lifted for movement, whereas a rollator has wheels and is pushed. A walker allows a slower pace while a rollator, with three or four wheels, features hand-operated brakes and may have a seat to use when resting.:
"A standard walker is a simple, lightweight device without wheels. A user must have enough arm strength to pick up the walker and move it forward one step at a time. Most therapists consider a standard walker the most stable solution for those needing a little extra help.
Two-wheel walkers, which provider easier mobility, are also available for use by a person who doesn’t need quite as much support but is not stable enough to use a four-wheel rollator."