The meta description is an HTML tag that provides a short and accurate summary of the webpage. The meta description is used by search engines to identify a webpage's topic and provide relevant search results.
The alt attribute specifies an alternate text for an image, if the image cannot be displayed. The alt attribute is also useful for search engines to identify the subject of the image, and helps screen readers describe the image.
HTTP security are a subset of HTTP headers that is related specifically to security. They are exchanged between a client (usually a web browser) and a server to specify the security details of HTTP communication.