The meaning of the speech is heavily debated but seems concerned with Hamlet’s hesitation to directly and immediately avenge his father’s murder on his uncle, step father and new king Claudius.
And as said above, the meaning is always debated. The debate, either about wordly affairs and management or in one’s mind about what one wants to be, to get in life? What career choices one must make? How much to enjoy and how much to save? To be as your society wants or to be free as you want to be? What action must one should take?
But just think for a second that this happens only when one has a mind. Nature: it does not think twice at all. When it has to rain it will rain, when it has to throw the chills around it will. The wind will flow, the rains will come, the plants & trees will grow on the ground.
We are mostly concerned about the repurcussions of our actions and that is why we think before we take a step; shall we take it or not? To be what we want to be or not to be? What if we take an action? What if we take a step towards what we want to be? What will happen next?