The MacBook cycle count defines how many times you run your battery to 0% and charge it back to 100%. If you plug your phone in at 50% today, charge it to 100%, then run it back down to 50% tomorrow, that is one cycle count. Newer MacBooks typically have 1,000 cycle counts. But older models may have 300-400. After exceeding the cycle count, you may need to prepare for a new battery because your existing battery may charge only to 80% or less of its capacity.