You don't have to be sorry to ask questions because the essence of the forum is to advance the course of Bitcoin and at the core of that is learning. Most of us came here as novice to Bitcoin and the technology behind it, we learnt from this forum and we are still learning even while we are investing.

To answer your question, lump sum buying means buying with all the money you set aside to invest in Bitcoin all at once instead of dividing it to buy at different price points or different times. For instance, if you plan to invest $1,000 into Bitcoin, you can either decided to buy it at once or divide the money into five or ten parts as the case may be, then buy it in parts as you have divided. Each other the methods of buying have their advantages and depends largely on the person doing the buying. While some people will prefer this lump sum buy reason being that they don't have time to be looking at the price to know when it drops or they don't want to log in regularly or it could be that their job does not allow them access to the internet regularly like miners and fishermen. They could just buy with lump sum.

Some also use the DCA method which requires dividing the capital into several parts and then buy for each part weekly or monthly as the case may be. The most important thing to consider in any of the method is if the funds you are putting into Bitcoin will allow you have peace of mind. I mean, if you have settled your basic needs and also set aside some emergency funds so that you will not be forced to sell your Bitcoin when you did not plan.