in this example, the Search 🔍, “To…”, “Subject” and “Message” boxes are text boxes.
You can use the mouse to click inside a text box to put the “blinking line” (text insertion point) into it — so that you can type into the text box.
A place for everything, everything in its place
Benjamin Franklin
Please note in the above example, that the recipient’s email address (mine!) has been typed into the “To…” box.