Essential Goal. This is a goal that you need to achieve with 100% probability or a probability of 1. Basically, you CANNOT have a shortfall.
Important Goal. This is a goal that is less important than essential. When you plan, this is a goal that you can accept that there is less than 1 probability that you are able to fulfil the goal. This means that in some poor economic sequence, the amount might fall short and you accept that.
Aspirational Goal. These are goals where the probability of being fulfilled is low to very low. With your current resources, it is likely you cannot fulfil them.