A textarea is a text box made for an answer that may need more than one line. It lets someone type a note, comment, or message and see several lines at once. It is like a small writing area in a paper form rather than a single blank line.
For example, a support page might ask, “How can we help?” and provide a textarea for the person to describe the problem. The box can often grow or let the person scroll as they type more.
Use a textarea when you expect a longer answer. Tell people what kind of detail is useful, but do not make them guess how much to write.