[crucialfelix]

In Buddhist meditation the initial exercise is almost always concentration meditation (samatha, breath meditation). This trains you in single pointed concentration, relaxing the mind on the object, skillfully dealing with distractions.

But that isn't the goal of Buddhist meditation, its the preliminary practice. You need those skills in order to release your fixation/concentration without just spacing out in a dull sleepiness.

After that you do various forms of insight meditation (vipassana) which can explore what the single pointed concentration is.

In Dzogchen there are alternating exercises of single-pointed concentration and then releasing the attention and observing all things (including observing the observer and the observation process). If a beginner observes "everything" they just get spaced out and dull minded. That's why you alternate the exercises.