Conversation View is a core feature of Gmail. You can choose whether replies to emails are grouped in conversations or if each email shows up in your inbox separately.
Conversation View in Gmail is when replies to emails are grouped in conversations to follow the conversation more easily.
Gmail users have a love-hate relationship with Conversation View - I personally don't like it but know others that can live without it. It can take a little time to get used to and there are dangers that important messages can be missed when emails are grouped together.
The Gmail Nudge and Snooze features which are amazing productivity tool, require Conversation View to be ON.
Nudge will suggest emails to reply to - Emails that you might have forgotten to respond to will appear at the top of your inbox and suggest emails to follow up on - Sent emails that you might need to follow up on will appear at the top of your inbox.
Snooze allows you to postpone emails and temporarily remove them from your inbox until you need them. Your email will come back to the top of your inbox when you want it to, whether that's tomorrow, next week or this evening.
Why use Conversation view
Conversation View groups email together and cleans up your inbox.
Benefit from the Nudge and Snooze AI and MAchine Learning Tools
You can turn conversation view ON and OFF from your Gmail Settings