Time Travel is the ability in which an individual or object literally moves through different points in time.
There are various methods of achieving time travel. One of the most well known is through the use of a Time Stone. Silver the Hedgehog, a frequent time traveller, uses one of these stones to initiate Chronos Control. (SU: #8)
In the unaltered Light Mobius timeline, Dr. Eggman had built a device known as the Tachyon Chamber before his defeat, which was capable of time travel. King Sonic used this machine to travel to the past in an effort to undo the damages he had caused to the space time continuum. He apparently succeeded, but at the cost of changing the timeline. (StH: #144, #166)
Those who travel into the past are capable of altering their respective present day timeline by initiating any event that would have a large enough impact on future events. In most of these instances, the time traveller who initiated these changes are shown to have retained their memories of how their timeline used to be. Silver's numerous travels to, and interactions in the past have caused his own future timeline to change to small degrees, with no recollection of any past events that occurred in his new timeline. (StH: #216)
While not strictly the same as travelling through different points in time, one of the known capabilities of the reality-warping Genesis Wave is making a reality excell forward through its timeline. When Dr. Eggman and Dr. Wily launched the second wave on their respective worlds, the timeline of Wily's home dimension of Earth 20XX had skipped forward by an unknown amount of time. MM: #24)