import re

text = "Contact us at sara123@gmail.com or call +91-9876543210"

email = re.findall(r"[a-zA-Z0-9._]+@[a-z]+\.[a-z]+", text)
print("Email:", email)

Email: ['sara123@gmail.com']

phone = re.findall(r"\+91-\d{10}", text)
print("Phone:", phone)

Phone: ['+91-9876543210']

Regex is used for pattern matching.
Useful in scraping, validation.