What is the purpose of the placeholder attribute?

The `placeholder` attribute is a property in HTML form elements used to provide placeholder text in input fields, which serves as a hint or example to users about the required input content.

When the input field is empty, the text in the `placeholder` attribute will be displayed inside the input field, usually in a lighter color. Once the user starts inputting content in the input field, the placeholder text will automatically disappear.

The main purpose of the `placeholder` attribute is to provide users with a brief hint on what type of information should be entered in that field. For example, in a login form, the username field may have a `placeholder` value of “Enter username” as a prompt. This helps users better understand the expected input content and enhances user experience and usability.

Here is an example demonstrating how to use the `placeholder` attribute:

<input type="text" placeholder="请输入用户名">

Please note that the `placeholder` attribute only provides a hint and is not considered as an actual input value. The content of `placeholder` will not be included in the form data when submitting the form. If you need to pass the default value as the actual input value to the server, consider using the `value` attribute to set the default value.