Let's say you're having a party, and you want to make sure there aren't too many people there, or else things might get too crowded and nobody will have any fun. The Engset formula is like a way to figure out how many people you can invite to your party without it getting too crowded.
Now, imagine that your party is really a phone conference call. And instead of people, you have phone lines. The Engset formula helps you figure out how many phone lines you can have in use at the same time without everyone experiencing a busy signal.
Imagine you have a certain number of phone lines available (let's say five). And you know that your phone call will last a certain amount of time (let's say one hour). You also know the average length of time that each person will be on the phone (let's say 10 minutes).
The Engset formula helps you figure out how many people can be on the phone at the same time without experiencing a busy signal by taking into account how many phone lines you have available, how long the call is, and how long each person stays on the phone.
Basically, it's like figuring out how many people you can invite to your phone conference "party" without it getting too crowded and causing technical issues.