These are used in creating template HTML files.
Jinja Segments
In app.py
@app.route('/')
def index():
    return render_template("index.html", myval="DAVID"In index.html
<body>
    HI {{myval}}
</bodyThe values will always typecasted as strings
Then

Jinja Blocks
Templates allow you to run python code within HTML.
index.html
<!DOCTYPE html>
<html lang="en">
 
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
	<ul>
		{% for item in mylist%}
			{{ item }}
		{% endfor %}
	</ul>
</body>
</html>