The definition of a close friend can vary from person to person, but generally, a close friend is someone with whom you have a strong and meaningful emotional bond. Close friends are typically individuals whom you trust, rely on, and feel comfortable being yourself around. They are the people you share your life with, confide in, and can count on during both good times and bad.
As for how well close friends know each other, yes, a key characteristic of a close friendship is knowing each other very well. Close friends often have a deep understanding of each other's personalities, values, interests, and life experiences. They have likely spent a significant amount of time together, shared stories and experiences, and have grown to appreciate each other's quirks and traits.
In terms of secrets, close friends often feel comfortable revealing more intimate details about themselves, as there is a strong level of trust and mutual support. While not every aspect of life needs to be an open book, close friends typically feel they can share their thoughts, feelings, and concerns without fear of judgment or betrayal.
It's important to note that friendships exist on a spectrum, and not all friends will be as close as others. Some friendships may be more casual and surface-level, while others develop into deep and lasting connections. The level of closeness in a friendship can evolve over time and may depend on the individuals involved and the shared experiences they have had.