sore: In this context, "sore" refers to pain or discomfort in Rachel's foot. She might be experiencing physical pain or tenderness.
Actually: Rachel uses "actually" to provide additional information or correct Mary's assumption. In this case, she clarifies that the sport is not tennis or basketball but rather a volleyball tournament.
tournament: A tournament is a competition in which participants compete against each other, often in a series of matches, to determine a winner. In this dialogue, it refers to a volleyball competition at the sports center.
That's so cool!: This is an expression of excitement and approval. Mary is enthusiastic about the idea of a volleyball tournament and expresses it by saying, "That's so cool!"
You bet!: This is an informal way of saying "definitely" or "certainly." Mary is expressing strong agreement and eagerness to play volleyball with the team.
pal: "Pal" is a friendly and informal term used to address a friend or acquaintance. In this case, Rachel uses it to thank Mary for agreeing to take her place in the volleyball match.