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.
Different meta tags are defined by changing the name attribute to a valid value. The most commonly used meta tag is the one used for descriptions: <meta name=description content=A general guide on the use of meta tags in html pages>. In cases of empty descriptions (or non-existent ones), search engines will generate a description from the content of the page. You can also set the author of a page using meta tags.