Speed refers to the rate at which an entity, such as a ship, or a laser is able to move across space. The max speed is different for each ship. The time it takes to reach this max speed or acceleration is determined by the agility of the ship. Lasers move at constant speed after the initial velocity is set.
A ship's speed is defined by the fastest it can go while going forward(left mouse button/forward arrow key). The ship has a maximum speed while doing this. As you may notice while using recoil(see U-Sniper and Shadow X-3) or getting knocked around by a Barracuda, you can exceed this maximum speed. The Friction setting will adjust how quickly you are brought back to still or moving at your maximum speed. Setting the friction at 0 in a Custom Game makes gimmicks like hyper speed possible.
Ship speed can be Upgraded with the red colored speed upgrade (marked with number 7).
A laser's speed affects how fast the laser moves if the ship is stationary. A unit vector in the direction of the ship is multiplied by the speed to create a direction velocity vector. The ship's velocity is added to this velocity, which then becomes the laser's initial velocity.
Faster laser speed results in more knockback when it hits a player.
Without being rammed or using recoil, the maximum possible actual laser speed is the sum of the ship speed and the laser speed. For example, if a maxed Fly is moving at max speed (145) forward and shoots its 180 speed laser, the total laser speed is 145+180 = 325. As another example, if an Odyssey was rammed and is moving backward at 100 speed, when it shoots, the laser will be stationary. If the Odyssey was rammed even harder and is moving backwards even faster, the laser will actually move backward.
Laser speed can be upgraded with the orange speed upgrade (marked with number 6).