Speed

Speed
Speed is simply how fast a character can move in a given amount of time. There are five types of speed used for VS purposes: Attack Speed, Combat Speed, Reaction Speed, Travel Speed, and Flight Speed. The term "Speed" normally refers to Combat Speed.

Attack Speed 

The speed at which an attack moves. For example, X character is hypersonic, but he can do an attack that is a natural beam of light, the speed for the attack is different from the speed of the user, hence the attack would be lightspeed even if its user isn't.

Combat Speed

The speed at which a character can fight.

Reaction Speed 

Reaction speed is the speed at which a character can react to an event or action. This usually only grants a short movement upon reaction, whereas several movements at the same speed switch it to combat speed.

For example, say that character A shoots at character B with a gun and character B dodges. That is reaction speed. Keep in mind, sometimes a person aim dodges and it is not as good of a feat.

As another example, let's say that character A uses a minigun on character B, but the minigun takes a second or two to charge up and Character B sees this. If Character B dodges it is considered aim dodging since he/she knew that the attack was going to happen.

Reaction speed is reacting to an attack that you don't know is going to happen, or at a very close range. The reaction speed of a character also tends to be higher than its movement speed.

Travel Speed 

The speed at which a character or object can move by running, or through similar means that do not involve flight or teleportation.

Flight Speed 

The speed at which a character or object flies a certain distance, like going from the earth to the sun for example.

High flight speed logically requires similar reaction speed in order to manoeuvre when approaching different objects.

However, certain franchises, such as Marvel Comics (and DC Comics or Image Comics, which follow the same conventions), make a great distinction between regular movement speed and flight speed

As such, we have generally assumed that the characters' regular reaction or combat speeds are roughly equivalent to their flight speeds, unless this is clearly contradicted.

Conversion
You can use this calculator to convert from one speed unit to another.

There is also this  calculator that you can use for ease of finding how fast your character is (in terms of time, speed, and distance) made to be depending what speed feat they've done. There you can also pretty much get the result of the speed, time, and/or distance your character managed to cover when getting to their destination, what attack or thing they reacted to, and so on.

There is this calculator that one can use to find the KE of a person or object going at Relativistic speeds (as well as other factors involving with it like time dilation and relativistic mass.). Read here when attempting to use this calculator type.

Speed Levels
Below Average Human (0-5 m/s)

Normal Human (5-7.7 m/s)

Athletic Human (7.7-9.8 m/s)

Peak Human (9.8-12.43 m/s)

Superhuman (12.43-34.3 m/s)

Subsonic (Faster than Eye) (Mach 0.1-0.5) (34.3-171.5 m/s or 76.7-383.6 mph)

Subsonic+ (Mach 0.5-0.9) (171.5-308.7 m/s)

Transonic (Mach 0.9-1.1) (308.7-377.3 m/s)

Supersonic (Mach 1.1-2.5)

Supersonic+ (Mach 2.5-5)

Hypersonic (Mach 5-10)

Hypersonic+ (Mach 10-25)

High Hypersonic (Mach 25-50)

High Hypersonic+ (Mach 50-100)

Massively Hypersonic (Mach 100-1000)

Massively Hypersonic+ (Mach 1000-8810.2)

Sub-Relativistic (1%-5% SoL)

Sub-Relativistic+ (5%-10% SoL)

Relativistic (10%-50% SoL)

Relativistic+ (50%-100% SoL)

Speed of Light

FTL (x1-10 Speed of Light)

FTL+ (x10-100 Speed of Light)

Massively FTL (x100-1000 Speed of Light)

Massively FTL+ (x1000+ Speed of Light)

Infinite Speed (Able to move while time literally stands still, or to travel anywhere instantly. Teleportation does not count)

Immeasurable (Movement beyond linear time. This is why the speed cannot be measured. Given that S = D/T, if T is undefined the speed formula cannot be applied. This is the same reason why multiple temporal dimensions also grant immeasurable speed)

Irrelevant (Characters beyond the concepts of dimensions themselves, including time. Meaning: Tier 1-A and above)

Variable Tier

Omnipresent (Higher-dimensional omnipresence of a certain plane of existence is superior to the immeasurable speed gained from existing on the same level. Similarly, immeasurable speed associated with a higher plane is superior to the omnipresence of a lower-dimensional entity. However, each case requires more detailed consideration.)