In Dual-pane file manager such as X‑plore, the highlighted pane is source for all operations, including copy/move. The other inactive pane is destination for some operations such as copy/move.
Use Switch pane function to select other pane, and choose desired destination folder. (There are more ways how to switch panes: fling screen left/right, or use button, or use keyboard shortcut.)
Then switch back to other pane from where you wish to copy, select folder or mark multiple files, and choose Copy (or Move) function.
Files will be copied/moved from source pane to destination pane. In image above, source is on left, destination is on right. If you wish, this may be other way, source on right and destination on left.
On smaller screens or in portrait mode, destination pane may not be visible, but it is still there, you see blue arrow and destination folder name at top, and all works as written above.
X-plore contains also traditional clipboard with Copy and Paste functions (and eventually also Move function).
Clipboard is used in two step operational mode. First mark file(s) to be copied, and put (copy) them to clipboard. So far nothing was copied, just remembered. Then select target folder where selected files have to be copied/moved, and use Paste button to copy/move the files there.
Mark files as usual, which also works on currently selected folder if nothing is marked. Then use Copy to clipboard function available on long-click, as button or keyboard shortcut.
When clipboard contains files (ready for copying) then it is displayed at bottom of screen and offers Paste button.
Sometimes the Paste button is grayed and not clickable. This is when target folder is not valid place for copying files, for example it is not writable, is same as source folder, or is a child of copied folder. When you select valid folder as target, the Paste button will become enabled.
Paste function is also available as button or keyboard shortcut.
As with copying between two panes, also in the clipboard you can select Move mode, where files are moved instead of copied. You choose this after copying files into clipboard, before pasting them.
After choosing Paste, actual copying begins, which is same with above described pane-to-pane mode. A dialog will be shown with collecting and copying of files. Sometimes it's so fast that it just flashes, sometimes it's long, and you can put the dialog to work in background.
You can discard clipboard displayed at bottom of screen by clicking X button at top right of its toolbar. This way it will be hidden and reset to not contain any files.
Clipboard is also discarded automatically when you mark some other files or leave X-plore.
In Configuration, you can set option to automatically show the Clipboard toolbar when you start marking some files.