Stakeholders include individuals and groups you interact with in and outside your organisation.
Effective at engaging stakeholders is a highly sought-after skill.
To 'engage' a stakeholder is to interact with them. You involve them in conversation with you. You are listening to them, asking questions, trying to get to know them on a deeper level, and working with them in a close and collaborative manner as professionals in the workplace.
It takes perseverance and a genuine interest in others to engage effectively.
When you want to build a strong working relationship with someone, you do your utmost to get to know them well.
You want to work effectively with them and build a strong working relationship with that person or group of people.
It takes effort. It takes perseverance and energy.
Being able to engage well with stakeholders is a highly sought-after skill because most jobs these days, probably 90% in fact, require the employee to some extent to engage with people both within the workplace and externally, such as with suppliers, and partners.
Many employers will highly value the ability to engage well with people, build rapport, establish and maintain relationships and nurture existing connections. You may even be asked this in an interview setting.