Extended definition
Open Graph equivalent for Twitter/X. <meta name="twitter:..."> tags.
Context and application
Twitter Cards have 4 types: summary (small, text only), summary_large_image (with large 1200×675 image), app (for app downloads), player (for video). For most sites, summary_large_image is the correct default. In practice, Twitter / X falls back to Open Graph if it doesn’t find twitter:* tags — so you can set only OG and it works on both. Twitter-specific tags remain useful for: twitter:site (brand account handle), twitter:creator (article author handle for attribution).