Floating is one of the settings you can attribute to a table or to an anchored frame.
When something floats, it means that the object that is anchored (as a table or an anchored frame) can move away from its anchor into another column. When something does not float, the anchor and the anchor's content must remain together -- at the very least, in the same column.
"Below current line" frames (BLC frames) try to fit just below the line in which the anchor appears; for example, if the anchor is in the second line of a four-line paragraph, it will sit between lines two and three. In most cases, you insert a BLC anchor at the end of a paragraph, just before the paragraph mark; this keeps a paragraph from being split by the frame (although sometimes this is desired).
If a BLC frame can't fit below the anchor in the remaining space (the space between the anchor and the bottom of the column), it will move to the top of the next column and drag the line containing the anchor along with it. Nothing more can appear in the column in which the anchor appears. Note that you can get all the lines to move with the anchor by using Window/Orphan=99 (or any sufficiently high number) in the paragraph's tag.
Top/bottom-of-column frames (TBC frames) try to fit themselves at the top or bottom of the column in which the anchor appears. Additionally, text that follows the anchor can fill the space between the TBC anchor and the bottom of the page (if the frame is at the top of the page) or the top edge of the frame (if the frame is at the bottom of the page).
The floating attribute makes an anchor behave as described at the top of this page.
Top tables (any of the four) always goes to the top of the next page, column, or whatever. However, no text is allowed below the anchor, other than what can fill out the rest of the line. Don't ever anchor a top table to the front of a paragraph. If you must use this type, the anchor should be at the end of the paragraph.
Like BLC frames, anywhere tables try to fit just below the line in which the anchor appears; for example, if the anchor is in the second line of a four-line paragraph, it will sit between lines two and four. If the table can't fit below the anchor in the remaining space and the table is set with all rows "keep with prev & next," it will move to the top of the next column and drag the line with the anchor with it. Nothing more can appear in the original column. If the table can't fit and the table is breakable, the remaining rows simply flow to the next page, and the text of the remaining paragraphs follow the last line of the table. If the anchor is at the end of the paragraph, you can get all the entire paragraph to move with the anchor by using the Window/Orphan=99 setting.
The floating table can break away from its anchor, allowing text to appear under the anchor.