Wipe, in a computing context, means  to render all data on a hard drive unreadable. The term is often used in reference to making data stored on a computer, smartphone or tablet inaccessible before disposing of the device.
A semantic HTML tag is one that defines a meaning to the enclosed content that a computer can be programmed to understand. In most cases, browsers create some visual difference to content in semantic tags, for example, content in the CODE element is usually displayed in a monospaced font. But this is not a requirement. Many people feel that semantic HTML elements are a waste of bandwidth.
The HTML <body> tag is used for declaring the main content section of the HTML document. The <body> tag is placed after the document's head (i.e. between the </head> and the </html> tags). The basic tag is written like this <body></body>, with the document's content inserted between the opening and closing tags. On any normal-sized HTML document, you'll usually see the opening tag (<body>) near the top of the document and the closing tag (</body>) near the bottom.