Android Lollipop is latest of Android family operating systems. It has better User interface, easy to navigate and fluid motion menu with better navigation.
It also has battery saver feature which claims to save up to 90 minutes. It shows approximate time left to fully charge.
Lollipop has SELinux enforcing for all applications that gives better protection against malwares.
You can access your device contents using another Lollipop device. You can create multiple users e.g. a guest user, so any one can use your phone as a guest user but cannot see your contacts, messages, pictures etc.
It also has improved network selection logic so better connectivity. Better performance and Android TV.