What causes the car to understeer and oversteer

Not sure if these are the right terms to use, just had the front end completely rebuilt except for the steering box.
The car tends to keep wanting to go in the direction of compensation, fighting it going back and forth, there’s about an inch of play both ways on the steering wheel,.
The mechanic told me it was the best he could do, he told me that if he adjusted anymore it started to bind.

Seems to be be a slight clunking sound if I rock the steering wheel back and forth