It is the plural form of "último", which means "last" or "latest" in the singular form.
Here are some examples:
* Los últimos días (The last days)
* Las últimas noticias (The latest news)
* Los últimos modelos (The latest models)
It's important to note that "últimos" is a masculine plural, so it would be used for things that are masculine in Spanish. If you are referring to feminine things, you would use "últimas".