There's a fine line between friendly and flirting. And it's important to read in between that line so you don't seem ridiculous if you decide to approach that person who is being friendly with you.
If a friend comes up to you and talk about nothing really important or they find an excuse just to get close to you for no reason at all, then maybe that person really likes you more than a friend would.
But if a friend starts a conversation when you only pass them by, maintains eye contact while discussing random things , then it simply means they are not flirting. They just love to be friends with you.
Even if you think this person is giving you a signal, it's better you wait, take your time and be sure they are into you first.
Watch a video by life coach and relationship expert Marie Dubuque as she explains better on this: