How do tanks steer?

How do they do it since they have fixed parrallel chains?
And can a tank turn while advancing?

I want a full description please.

They are able to steer even better than vehicles with wheels. They do it by making one track move faster than the other. Most tracked vehicles are capable of making 360 degree turns in place by making one track go forward and the other track backward.

To amplify what aeropl posted:

Tracked vehicles turn by locking one of the tracks while the other moves. Thus if you are moving forward want to turn right, you lock your right track and basically pivot on it until you are at the heading you want. Some vehicles, such as the Bradley IFV and the M113A2 & A3, have a pivot turn that will allow them to turn in place.

So, yes, a tank may turn while moving forward or backward.

You don’t really need to LOCK the track. “Lock” to me means that track is not moving at all. As long as one track is moving slower than the other, the vehicle will turn towards the slower track.

The one time I got to play with a small Cat dozer I did find it easier to pivit on a locked track. However an experienced operator, not me, can make sweeping or gradual truns by slowing one track.

Needless to say that turning a tracked vehicle on the spot tends to chew up the ground somewhat, as only the midpoints of each track will actually be decribing a circle; other points on the track are being dragged sideways somewhat.

Not that this tends to matter all that much in time of war.

Those small ‘Bobcat’ type forklift/ front end loader vehicles steer the same way as a tank, by turning the wheels on either side at a different speed. When turning on pavement or concrete there is quite a bit of tire scrubbing. I have heard this type of steering called ‘skid steer’ but I am not sure if that is an official term.

This link has a video of a skid steer in action and apparently that is an official term.