Use J in normal mode to join the current line that the cursor is on with the line below.
You can also use J in visual mode to join all of the selected lines onto a single line.
The same operation can be done from the command line with the :join command, which can be especially useful when combined with the global command.
Try it in the editor — combine the paragraphs onto a single line using the J key in normal and visual mode. If you’re feeling adventurous, you can also experiment with the :join Ex command!