This help page describes how to switch between entering text and math in a document block.

In the quick access toolbar, the current mode is indicated.

To switch entry mode:

On the quick access toolbar, use the drop-down box to select from Math, Text, and Nonexecutable Math.  This is also found on the Edit tab of the ribbon, in the Input Configuration group, under Mode.

Alternatively, use the F5 shortcut key, which toggles between these three modes in sequence: Math, Text, and Nonexecutable Math.

In the quick access toolbar, the mode indicator switches to the new mode.

Note: At a Maple prompt, this mode selector allows you to switch between 2-D math and Maple Input (also called 1-D math) modes.  In this case, "Text" applies to Maple Input.  See also Select Entry Mode at Maple Prompt.