Big Deal Alerts are notifications that are sent to users when an opportunity reaches a certain amount, probability, or stage. They can be configured by administrators to alert sales reps or managers when they have a high likelihood of winning a big deal. Key Deals are a feature of Einstein Opportunity Scoring that shows the top opportunities based on their score and stage, but they do not send notifications. Activity Timeline is a component of Lightning Experience that shows the past and upcoming activities related to a record, but it does not notify users of big deals. Performance chart is a type of report chart that shows how well users or teams are performing against their goals, but it does not alert users of big deals. References: https://help.salesforce.com/s/articleView?id=sf.forecasts3_big_deal.htm &type=5