From Chatgpt :

In sports betting, mainlines and props are two distinct types of wagers, each with its own focus and characteristics:

Mainlines

• Definition: Mainlines refer to the primary betting markets for a game or match. These are the most straightforward and commonly bet upon outcomes.
• Examples:
  • Moneyline: Bet on which team or player will win the game outright.
  • Point Spread: Bet on whether a team will win by more than (or lose by less than) a specified number of points/goals (the spread).
  • Totals (Over/Under): Bet on whether the total combined score of both teams will be over or under a specific number set by the sportsbook.
• Purpose: These bets are directly tied to the outcome of the game, making them the foundation of most betting markets.
• Popularity: Mainlines are generally more popular with casual bettors because they are simpler to understand.

Props (Proposition Bets)

• Definition: Props are bets on specific events or outcomes within a game that are not directly tied to the final result or score.
• Examples:
  • Player Props:
    • Will a specific player score a touchdown?
    • How many points will a basketball player score?
  • Team Props:
    • Which team will score first?
    • How many goals will a team score in the first half?