SARMs are androgen receptor modulators. In simple terms, these substances act on receptors like testosterone, causing muscle growth, increased fat burning, and also contribute to increased endurance and strength.
SARMs are marketed as substances without any unpleasant side effects. At least this applies to non-steroidal forms. How can this be? The most popular explanation for this is that they have a "selective" effect. That is, they only purposefully act on androgen receptors and, due to this, cause a set of muscle mass. In other words, their effect is pointwise, and not on the whole organism. At the same time, it is said that there are no such side effects as steroids when taking SARMs.