Cross promotion is a mobile marketing technique to let app developers with a large portfolio of apps promote their apps in another app of theirs. It is a common strategy among game studios with plenty of games in their portfolio. It helps them to monetize their users in different apps and to keep their users within their portfolio. 

If cross promotion strategy is not executed properly, it can cause loss of users from the portfolio and it can increase churn rate. User experience and user behavior should be understood very well before making the cross promotion strategy live.