What is the best soil to put in a planter?

Could you please elaborate on what factors should be considered when selecting the best soil for a planter? Is it the type of plant being grown, the size of the planter, or the climate conditions? Additionally, what are the benefits of using organic soil versus synthetic soil, and how does the soil's drainage capabilities affect the health of the plants? Understanding these aspects would help me make an informed decision when choosing the best soil for my planter.