Obsolete means no longer useful or needed because something better has replaced it. When technology becomes obsolete, people stop using it because newer inventions do the job better, faster, or more easily.

Think about floppy disks, those square plastic storage devices people used to save computer files on in the 1990s. They held far less information than a USB drive, broke easily, and worked slowly. Once USB drives and cloud storage appeared, floppy disks became obsolete. They still worked, but nobody wanted to use them anymore.

Obsolete things aren't necessarily broken or bad. They just can't compete with what came next. Typewriters became obsolete when computers offered easier editing and printing. Film cameras became obsolete for most people when digital cameras let you see your photos instantly and take unlimited pictures. The horse and buggy became obsolete when cars arrived.

Sometimes skills become obsolete too. Knowing how to use a slide rule (a calculating tool) was once essential for engineers, but calculators made that skill obsolete. Other skills, like critical thinking or clear writing, never become obsolete because nothing can replace them.

When something is obsolescent, it's in the process of becoming obsolete but isn't obsolete yet.