is schema really help in seo? and what it is used for?

Schema is very important in seo. Schema defines the type of content to google. With the right schema google identifies the type of content for example if you post job posting or any product then its important to add a schema of it so google will know what it is. There are many types of SEO like blog schema, news, article, product, job etc. Generating schema is easy, on wordpress you can make it with plugins like Yoast or rankmath. There are also several websites to generate schema. Just google online schema generators and there you go. What are your thoughts on this?

It is a ranking factor, but the key role is to increase click through rates for the websites appearing in the search results.

The main issue is when does google index them and show on front end.

It is not a ranking factor. You can get better positions by using it, faster, but thats because Google can place your content in their index faster - and even sometimes in better positions.