Many times in literature I read that Radar is used to detect objects. How does this work? Are reflections from objects with Radar not point reflections? And how does Radar know that all reflections belong to a same object when it is close to another object?
Mostly by keeping the beam narrow. If the outgoing beam is very thin then it is only likely to hit one object at a time - because only one target fits in the beam. A wider beam might have reflections from many objects.
Another technique is to use the radar to measure the speed of the object. The frequency of the signal reflected from an object moving away/toward the radar is shifted slightly. It is possible to measure the change in the returned radio frequency (compared to the outgoing pulse) and so measure the speed of the target. If you have several returns with different speeds you know each return was from a different target.