In simple terms, "Mentally Somewhere Else" means that your thoughts and focus are not where you physically are. It's like when you're in a class or a meeting, but your mind is thinking about something completely different, like what you'll have for lunch or a fun weekend plan. It's when you're present in body but not in mind.
Imagine you're in a beautiful park, but you can't enjoy it because you're thinking about work or a problem you need to solve. That's being mentally somewhere else. It can happen when you're daydreaming or when something is bothering you, and you can't concentrate on what's happening around you.
Being "Mentally Somewhere Else" can have its pros and cons. On one hand, it can help you escape from boring or stressful situations, but on the other hand, it might make you miss out on important information or experiences. So, it's essential to strike a balance between being present mentally and letting your mind wander when it's appropriate.