These are the solid walls in 5 different shapes.

These are the decorative walls. You can fly through them. However, since 4.4.0 these blocks can also be used as frictionblocks. This means you can still fly through them, but they will slow you down.

When you get close enough to these blocks, you can refuel by pressing <RIGHT_CTRL>.

Watch out, for these things can kill you. When you come near enough, they will start shooting at you. On some servers the cannons can be flakguns. This means that the bullets they fire will explode, creating a small dense cloud of bullets.

This is where the players begin. If you don't like your base, you can land on another base and press <HOME>. This is tricky though, since you have to be real close.

When you fly into this mapelement, it will instantaneously transport you to another part of the map.

You will be able to find more items near this mapelement then elsewhere in the map.
On some maps the itemconcentrator may not be visible.

Asteroid are more likely to appear near this mapelement then anywhere else.
On some maps the asteroidconcentrator may not be visible.

Most maps already have gravity of their own, but these map elements can push you around too.

The arrow pushes you in the direction it points at.
The round arrow does that too
The + in the circle pushes you away.
The - in the circle pulls you toward it.

On some maps gravity can be invisible.

These blocks are like the blue blocks, only you can shoot them. You will see a X appear inside them, which grows larger everytime you shoot them. Once the X is as big as the target, it explodes.
The target is usually used in teamplaymaps, but it can be used in other maps as a breakable wall too.

Inside the treasurebox there usually is a treasure or ball as it is usually called. If you touch the box you will die so keep your distance.