An older person is a senior citizen or someone who's been around long enough that they're not considered "young." If you want to check out some older people, take part in the early bird special at your local diner.
You can use the adjective older to describe elderly folks (like your older neighbors who don't drive at night any more) or a person who was born first: "Her older sister was much bossier than her younger sister." You can also use older to talk about things that have been around longer, like older songs or older cars, as opposed to newer things.