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.
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.
The speed at which a character can fight.
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, let's 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.
The speed at which a character or object can move by running, or through similar means that do not involve flight or teleportation.
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.
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.
You can use this calculator to convert from one speed unit to another.
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 the 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 (The ability to move infinite distance in finite time without the aid of teleportation.)
Inaccessible (The ability to move distances, whether finite or infinite, in zero time without the aid of teleportation. This is usually achieved by moving in places outside of time or places where time doesn't flow.)
Immeasurable (The ability to move at a speed unbound by linear time entirely, and thus cannot be measured using the basic speed formula.)
Irrelevant Being so fast that the concept of speed is irrelevant. Speed qualitatively beyond the concepts of distance and time, exceeding the entirety of the speed formula itself. Note while it is uncommon, it isn't impossible to achieve this speed while not being 1-A or above.
NOTE: The reason why Omnipresence isn't treated as a speed here is because it isn't really a speed, but a state of being. In fact, Omnipresence is the property to be present everywhere and anywhere at the same time or the state of being widespread and constantly encountered. However, technically any living being would be considered to be present everywhere or anywhere throughout their entire body and they would fulfill the definition of being everywhere at the same time. While speed only refers to the ability to move and operate, a state of being relates to the physical condition of a person and is a part of their physical self. If a character is omnipresent, they could literally be attacked everywhere and anywhere and they would be hit every single time, because they wouldn't be able to dodge said attacks due to their physical condition of existing in all the places at once.