Meaning of the constants that appear in the Master Theorem
That is not the general formula for time complexity. There is no "general formula  for time complexity", any more than there is a "general formula for the answer."

Rather, the formula you give is a recurrence relation that can be used to compute the running time of certain divide-and-conquer&ndash;style recursive algorithms.  Specifically, it corresponds to a recursive function which, when given an input of size&nbsp;$n$, makes $a$&nbsp;recursive calls, each on inputs of size $n/c$. If you pretended that the recursive calls were "free" (i.e., that they returned their answer in one computation step), then the algorithm would take $bn^k$ steps.