how to use render_template, explain in detail

render_template is a function in Flask that helps to render HTML templates from the application's templates directory. It is used to generate HTML pages dynamically based on user input, database content or other factors.

Here is how to use render_template in Flask:

First, import the function from the Flask module:
```
from flask import Flask, render_template
```
Then, create a Flask application instance:
```
app = Flask(__name__)
```
Next, create a view function that returns the rendered template:
```
@app.route('/')
def index():
    return render_template('index.html')
```
In this example, the index() function is associated with the '/' route. When a user visits the root URL of the website, the function is called and it returns the rendered 'index.html' template.
Create an HTML template file in the application's templates directory. In this example, we created a file named 'index.html':
```
<!DOCTYPE html>
<html>
  <head>
    <title>My Flask App</title>
  </head>
  <body>
    <h1>Welcome to my Flask app!</h1>
  </body>
</html>
```
This template is a basic HTML file that contains a title and a heading.

Finally, start the Flask development server:

if __name__ == '__main__':
    app.run(debug=True)

This is a basic example of how to use render_template in Flask. You can pass variables to the template, use control structures like loops and conditionals, and include other templates within a template. The possibilities are endless!

how to use render_template, explain in detail