A credit limit in Twitter ads is the maximum amount of money that an advertiser can spend on their Twitter ads within a specific time period. This limit ensures that advertisers do not overspend and helps them to budget their ad campaigns effectively. When setting up a Twitter ads account, advertisers can set their credit limit based on their budget and the duration of their ad campaign. Once the credit limit is reached, Twitter will stop serving ads until the advertiser makes a payment to replenish their account. It is important for advertisers to keep track of their credit limit and adjust it accordingly to avoid any disruptions to their ad campaigns. By managing their credit limit effectively, advertisers can maximize the impact of their Twitter ads and achieve their marketing goals.