According to Gege Akutami himself, Limitless operates the same way convergent and divergent sequences do in mathematics. No matter how many times you divide a number it will never be reduced to zero. In the same way, Limitless prevents someone from reaching to the user no matter how close they get. The impenetrable space between the user and their opponent is known as the "Infinity" (無限, Mugen).
Limitless allows the user to manipulate "Infinity" which in turn allows them to distort space. The user can not only slow down moving objects, but they can also create spaces with a gravitational pull as well. They can teleport too, but this can only be done under certain conditions.
Limitless is a hereditary Cursed Technique. However, it is extremely difficult to use and requires sophisticated manipulation of Cursed Energy. Although there are other Sorcerers capable of using the Limitless, Satoru Gojo is the only one who can master it because he possesses a special eye.
Limitless is the most powerful Cursed Technique currently known in the Jujutsu world. It has only been mastered by Satoru Gojo, who is considered the strongest individual in the entire world. Even Special Grade Cursed Spirits and Curse Users are unable to land a single attack on Gojo because of the Infinity barrier between them.
Not only does the Limitless provide impenetrable defenses, but it is also a potent offensive technique literally infinite potential uses. Gojo can suspend himself in mid-air, he can teleport, he can sever limbs with just a gaze, and he can even resist any attack a Special Grade Cursed Spirit like Jogo throws at him without a scratch.
The only true countermeasure to Gojo's Limitless is bringing him into a Domain. Domain Expansion grants a buff to its user and forces all of their attacks to hit their mark, effectively nullifying the Limitless's defensive capabilities.
Poisons are hard to pick up on.
Additionally, prolonged usage of the Limitless can have dangerous side effects for the user, such as frying your brain if you leave it constantly active (but Gojo Satoru runs a simultaneously self-recovering reverse technique, that way his brain will always stay fresh).
Satoru Gojo has mastered the Limitless to such a degree that its active almost all times of the day. This creates an impenetrable defense that prevents any harm from coming to Gojo. He casually uses it to teleport all the time, often confusing people he's traveling with.
Even the advanced Cursed Technique of a Special Grade Cursed Spirit like Jogo was rendered completely useless against Gojo. Jogo believed he hand landed several hits in their fight because he could feel that they hit the target. However, all he was actually hitting was the infinity between him and Gojo.
Offensively, Gojo uses the Limitless to move at extreme speeds, allowing him to quickly overwhelm his opponent with successive physical blows. He can also bring the divergence and convergence of infinity into reality using a Cursed Technique Reversal. If he wants to finish a fight quickly against another human, Gojo can instantly sever their limbs by distorting the space around them, causing instantaneous and brutal separation of appendages from the body.