Visual selection is a common feature in applications, but Vim's visual selection has several benefits.
To cut-and-paste or copy-and-paste:
Visual selection (steps 1-3) can be performed using a mouse.
If you want to change the selected text, press c instead of d or y in step 4. In a visual selection, pressing c performs a change by deleting the selected text and entering insert mode so you can type the new text.
Pasting over a block of text
You can copy a block of text by pressing Ctrl-v (or Ctrl-q if you use Ctrl-v for paste), then moving the cursor to select, and pressing y to yank. Now you can move elsewhere and press p to paste the text after the cursor (or P to paste before). The paste inserts a block (which might, for example, be 4 rows by 3 columns of text).
Instead of inserting the block, it is also possible to replace (paste over) the destination. To do this, move to the target location then press 1vp (1v selects an area equal to the original, and p pastes over it).
When a count is used before v, V, or ^V (character, line or block selection), an area equal to the previous area, multiplied by the count, is selected. See the paragraph after :help
Note that this will only work if you actually did something to the previous visual selection, such as a yank, delete, or change operation. It will not work after visually selecting an area and leaving visual mode without taking any actions.
* Visual selection
* Copy, cut and paste