The TextBox control is an input control, which allows a user to enter text to an application at runtime. By default, it allows only single line text; however, you can change its property to accept the multiline text as well as scroll bar also.
The RichTextBox control is similar to the TextBox control with the difference that it allows the user to format its text also. You can format the text in various ways, such as bold, italic, and underlined as well as change its color and font. You can save your RichTextBox value to a RTF (Rich Text Format) file and load value of RTF file to the RichTextBox control.