When it comes to web application, speed is matter and why it matter. When you speed up service, people become more engaged - and when people become more engaged, they approach more services and product.
Performance is about retaining users.We want users to interact meaningfully with what we build. If it's a blog, we want people to read posts. If it's an online store, we want them to buy stuff. If it's a social network, we want them to interact with each other.
While delivering content to visitors it's need more accurate speed and performance at a same time so we need to mainly focus on accuracy