Community engagement, in a nutshell, is all about crafting a coherent set of processes to nurture the members and investing in member development. This boosts the number of active people are in your community. An active community builds more value and helps members create stronger relationships.
The best way to encourage engagement is to ensure your community has a clear, worthwhile purpose. If this is the case, engagement will often occur organically.
Beyond this, community managers can encourage engagement by seeding content and organizing AMAs, webinars, or discussions. Good moderation also helps, as it ensures conversations stay valuable and on-topic.