Normally called "tie rod ends". There's an inner one and an outer one on each side of the car. The pair are the steering linkage that connects the rack and pinion steering gear to the spindles / wheels. Where the inner and outer are screwed together is the "toe" adjustment for the alignment. That adjustment is one of two that are critical for good tire wear and proper handling. Any looseness that develops in those joints will cause tire wear, steering wander, and will make it impossible to correctly adjust the alignment. The outer joints wear faster than the inners. The outer tie rod ends are very easy to replace with no special tools needed, but the car will have to be aligned.