A “tell” is non-verbal communication that gives information about what people may be thinking or feeling. Since we are often not aware of them, “tells” are often more honest than what people may actually say.
The moment someone sees you walk into the room, they may give a tell. If someone raises their eyebrows when they first see you, it is usually a sign that they genuinely like you. This should not be confused with surprise, which will include an opening of the eyes (and often the mouth as well).
On the other hand, squinting can be a sign that they do not like you. Squinting is a form of eye-blocking (covering or closing the eyes), which is a natural response to things we dislike or fear.