Of course, you can also say, "Hey, Google" to get the Assistant listening.
But don't worry if you don't have the feature yet.
This feature is now only available in English in the US, UK, Canada, and Australia.
While peppering our sentences with multiple "ands" sounds a bit weird, it does bring us a step closer to natural language commands, which will make interacting with voice assistants more like conversing with humans. This will "wake up" Google Assistant and make sure it's listening to you. For instance, you will be able to say, "Ok Google, switch on the lights and play music and turn up the volume", all in one go, and Google Assistant will do all that for you.
You can't use this feature if any of your commands require further clarification. For example, instead of saying "Ok, Google, what's the weather in NY and what's the weather in San Francisco?", you can simply say "Ok, Google, what's the weather in NY and San Francisco?".