Gyroscope / 3D accelerometer

Luk am wrote:
> hi
>
> what is the difference between a 3-axis gyrometer and a 3D
> accelerometer?

An accelerometer is meassering acceleration (e.g. 9.81g), a gyrometer 
the "spin rate" (a value like "10 degrees per second").

> if i have 3 situations:
> 1.) my object is lying horizontal on the table, not moving

One axis of the accelerometer will show 9.81g (the earth acceleration).
By this you can determine which side is facing the ground.

> 2.) my object is lying in a angle on the table, not moving

Same as above, but accerelation will be split on two axis.
You can determine the ground facing side using trigonometry.

> im planing to build my own quadcopter. id like to programm it with a
> microcontroller (basic knowlage of c and c++ and a lot of motivation ;)
> ) and the information source of a sensor like one of those.
> what do you suggest me to buy?

Short answer:
You'll need both of them.
Please use Google first - there's a whole lot of explanations.

Davis wrote:
>> One axis of the accelerometer will show 9.81g (the earth acceleration).
>
> The meter will schow 1 g or ca. 9,81 m/s²

Of course it will :D
Sorry for causing confusion ^^