Floating blocks is just a technical name for your graphs and figures, specifically describing the way that they relate to the surrounding text.
When you create a chart, graph or table, you want it to remain next to a specific piece of text.
Otherwise, as you add and remove text, it will appear on a different and completely unrelated page, making it very confusing for the reader. They may well become bored with flicking backwards and forwards through the paper, and will look for their information elsewhere.
If you insert a table or chart, then it automatically moves with the text, and you can decide how large it should be, and whether it interrupts the text or drifts to the side of the page.
However, inserting a figure with Microsoft Word has one big weakness, and that is that the caption does not move with the table. The only way to do this is with a workaround, where you create a text-box inside a drawing canvas.
This method avoids most of the problems associated with creating floating blocks, although it can be a little tortuous. If you have any difficulties, the help guide incorporated into the Word program is very useful.
The problem with Word is that the program has many problems with floating blocks, and can tend to hide chunks of text, or move your objects to strange places. Sadly, there is little that you can do about that, other than make sure that you proofread and check everything very carefully.