iOS 11 has a quick way to share your password (though you should, of course, do this with care). When someone is using the same Wi-Fi network your phone is on, you'll get a notification.
By tapping "send password," they can get on the network without having to manually enter complicated passwords. To make this work, both users need devices running iOS 11 with both Wi-Fi and Bluetooth turned on.
(This how-to is based on my experiences and info on Apple's support pages — where the images sometimes come from.)