Like all cells, the production of electricity is a chemical process. In primary cells, it is one way, once the process is done, so is the cell. In a rechargeable cell, the chemical process can be reversed, in effect 'putting electricity back into the cell'. But that process can only happen so fast, and putting more current into the cell than it can process will damage, and may destroy the cell.
There is a measurement called 'C', which is basically the capacity of the cell in milliamps over time (mAh). When charging a rechargeable cell, the rule of thumb is to use no more than C/2 current, and usually less. So for the larger cells like an 18650 or 18500 anything up to a one amp charging rate will work, with a lower rate obviously requiring a longer time. Smaller capacity cells like 18340 or 16340 (RCR123) or 14500 should be charged at no more than 0.5 amps to prevent damage. I currently use an Xtar VC4 charger, which will correctly charge all of the above, but not my 10440 cells, which need a lower charge rate than it provides. So I am going to have to dust off my Nitecore i4 charger to recharge those, since it does have a lower charge rate. Somewhere in the user manual for your charger there should be a section that describes the charging rates available, and the size cells the charger can safely recharge.