Sadly, no one has ever successfully demonstrated in front of reliable witnesses that telekinesis actually is possible. It's one thing to gather and move energy, but using simply psy energy to more a physical object seems to remain in the realm of impossibility.
A psi ball is much more about visualization and energy manipulation. It's a way to practice feeling the flow and concentration of whatever your concept of energy happens to be, and pooling it into a single space -- in this case, between the palms. The person generally visualizes how they believe that bundle of energy would appear, with the goal of making that vision in their mind's eye as realistic as possible. Some people eventually begin using psi balls in what some call bubble energy, which is simply putting whatever kind of energy (loving kindness, healing, positivity, hate, pain, etc.) into that energy ball, and projecting it either away and into the universe or to some remote target.
Sadly, the idea that a psi ball can be used to affect physical objects began being popularized while Naruto was first being aired some decade or so ago*, and has since been a concept integrated into the vast and growing lexicon of extremely abstracted practices which some people will insist are necessary to a magical practice (hint: most are not an absolute necessity) without even being able to explain who or how to use it for any sort of applicable process.
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*Naruto first aired in Japan in 2002, and within a very short time (thanks in part to the vast number of fan subbing groups) it had a dedicated following in the US, thanks also to fans of the manga; it did not start airing in the US until 2008. The concept of the main character's air-element energy balls were the primary inspiration for the popularization of psi balls at that time as it provided a visual example of what some people were describing at the time. There was also a popularization of Psionics thanks to that latest edition of Dungeons and Dragons and the introduction of the Mind Flayer at that time. Of course, some people had been using similar methods for their magical practices, and just like people still use certain scenes from Avatar, the Last Airbender, to help give examples of the seven-chakra system and energy flow, the same was done with Naruto. And just like Avatar, some people took it a bit too seriously. Sometimes what has been started is not so easily put to rest.
