Speed Force
The Speed Force is the energy within the Microverse (aka the Quantum Realm) that regulates the acceleration of native matter/particles between two points. Due to peculiar physical properties of the Quantum Realm, the energy needed to generate any momentum is the same regardless of mass inertia. Translated into physical reality, this manifests as perfectly metered power that is delivered at a significantly increased rate to the physical world. The Speed Force is the energy that holds the walls of the Quantum Realm together.
Speedforce users gain a suite of common powers associated with their interaction with the Speed Force. As well as simply moving fast they are protected from the effects of the incredible speeds they move at by the Speed Force aura, and while using the speed force think and react at a similarly accelerated rate. While using the speed force, speedsters will heal at a suitably accelerated rate too, though it should be observed this is an acceleration of the natural healing process. There is thus no regeneration, and correct healing may rely on proper bone-setting etc. The effective acceleration of subjective time also allows Speedsters to read and learn information at super speeds, however this is somewhat limited; information gained rapidly through use of the Speed Force will fade rapidly without the normal reinforcements to lodge information into long-term memory, and there are no shortcuts for that except one: Bart's photographic memory grants him near-perfect recall.
More experienced speedsters can learn other tricks: vibrating the molecules of their body to render themselves intangible and pass through walls, creating air vortices by running in circles, controlled utilization of the speed force aura to create electrical discharges, mainlining the Speed Force for enhanced strength, and lending speed to or stealing speed from other people. Only the most experienced are skilled at all of these. Some speedsters with a particularly close connection to the Speed Force have been able to use it to time travel or hop dimensions, but none can do this reliably (I.E. this is a Tiny Plot power!) and it involves serious risk of ending up lost inside the Speed Force.
It should be noted that these powers rely on connecting to the speed force. It takes a second or two for a speedster to accelerate enough to tap into it fully, and this provides a brief window of vulnerability. This doesn't mean they can't dodge bullets of course. A Speed Force user is still very fast as they're accelerating, but it does give a brief window where other particularly fast people can briefly compete. Think of Deathstroke reacting fast enough to trip Wally, or Superman speedily grabbing Barry's wrist just before he hares off somewhere.
One constant characteristic of speedsters that continues even when not actively using the Speed Force is their accelerated metabolisms. The biological variation required to allow a speedster access to the Speed Force requires a lot of extra energy, and speedsters need to eat a whole lot more than most!
