It's not new that you can do your Google voice searches. For some time now, browser has provided a small microphone next to the text box that you use a million times a day. When clicked, the user simply tells Google what he is looking for and the search engine does the trick. The problem is that clicking a button to talk isn't exactly very practical and many people just end up choosing to type it all in at once and hit "Enter".
Aware of this, Google announced the availability of an extension for Chrome that, once installed, allows people to say "OK, Google" to activate the voice input mode and speak their search terms.
The feature is not that new. It has been present on Chrome OS, Android and iOS for some time and comes to Chrome with some limitations, such as the need to access the address google.com
Even so, the experience is still valid, as the extension allows you to do some pretty cool things. You can for example record a reminder, convert units, translate words and even set a timer so you don't forget that lasagna in the oven.
Another nice thing is that Chrome starts to understand the context of your questions. For example, ask "Who is the president of the US?" and then "How old is he?" that Google will understand that "he" is Cyril Ramaphosa and will answer your question using the Knowledge Graph. Interestingly, if you type these same questions, Google won't understand the context and won't know how to answer.
To privacy concerns: Google informed that the extension will only send something after you say "OK Google" and that the entire process of detecting the keywords and analyzing them is done offline and locally on the user's computer.