That is a decently good explanation Joeboy - except when you say that they are completely two different things, you might contribute to confusion, since many times people will use terms interchangeably even though they have slightly different meanings.

Sometimes the use of one term or the other is not going to make any differences in the points being made and other times there can be a difference to talk about differences.

If we look at the word discretion - it just indicates something that you can decide to do whatever you want with it.  Sometimes a person might have limited discretion within guidelines and other times he will have complete discretion.  Many times when we are dealing with our own money we have quite a bit of discretion, unless we are in a relationship, then we might have obligations to people within our relationships.. yet many times we use the term discretion to suggest that the person has quite a bit of latitude in deciding how to use funds that are discretionary..

So yeah, as a few members have already mentioned we can think about various kinds of funds that we have available currently or we can consider funds that we might have in the future.  If we are receiving such funds in the form of a regular income then we might be referring to that flow of funds that are coming in and part of our income is non-discretionary, meaning that it has already been allocated for our expenses, and other funds are discretionary meaning we can do what we like with them.  So even if we are talking about our expenses we might talk about expenses that we have to pay, and they may be dealing with paying for our basic needs  such as food, lodging, utilities, water and maybe even transportation to and from work, versus expenses that are  discretionary such as going to a fancy restaurant or buying cigarretes or alcoholic drinks.

Sometimes we will use terms in vague and ambiguous ways and other times we might be trying to make certain kinds of points, so if we are talking about whether we need a steady income or not to buy bitcoin, then we might we might have some differences of opinion about that in terms of whether we are talking about what we might need for a one time purchase versus what we might need if we were to continue to want to buy bitcoin on a weekly basis.  If we don't have any back up funds, then we are totally reliant upon money that comes in to figure out what we are going to do with it and if there is extra after we had accounted for our basic expenses to be able to buy bitcoin.

Surely if we have various kinds of back up funds and even other investments then we might have more options, since we can draw from our back up funds to buy bitcoin.  Back up funds might be considered as emergency funds, reserve funds and float, and so usually we would not take from our emergency funds to buy bitcoin, so we might have had put limitations on how we are able to use our emergency funds, which we might say that they have limited discretion, yet since we created the rules for ourselves, we can still break the rules upon our discretion (upon our choice).  The reserve funds can be used for anything including buying bitcoin, so we might say that the reserve funds have full discretion in how they can be used, yet if the only money that we have available in our reserve funds is money that we had allocated to buy our daughter a bicycle once the funds reach $350, then we have limited discretion regarding those funds, even though we could break the limitations and decide to use the money for buying bitcoin rather than using that money to continue to save up for the bicycle for our daughter.

Discretionary funds could come from the income each month or it can come from money that is saved in our back up funds, and surely we can set up our bitcoin buys so that they are the same amount of money each week that is coming out of our regular income (such as $100 per week), so there would be a presumption that we have at least more than $100 of discretionary income each week and we are not spending from our non-discretionary income (money we need for expenses), yet if we don't have a regular income, then we may well start to deplete whatever funds that we have, which might mean that we either have to reduce our weekly buys or discontinue them... Of course, there are guys who have steady incomes and guys who do not, and some guys have more certainty than others in regards to their abilities to generate income in the event that they were to lose some or all of their current income sources.