If you are creating an event which potentially involves a meeting with others, then you can use the Calendar app to invite them. When the event is being created, you can scroll down to where it says ‘Guest’.
From here, simply start typing the guest’s name (if it is in your People app, the address will be filled in automatically) or manually input their email address and tap Return. When you click Done at the top, an email invitation will be sent to that person. You can then check on the invitation status by tapping on the event or via the notifications bar (Gmail messages).