Pattern Attribute in <input> tag

Question

I want to know
1. How to use pattern attribute inside input tag.
2. What should be the Value of pattern attribute.

Answer 1

The pattern attribute is used inside the input tag anywhere, for example <input type = "tel" pattern = "2- [0-9] {3} - [0-9] {3}" The numbers in this attribute are called "regular expressions" they can be found in the expression table.

Answer 2

http://htmlbook.ru/html/input/pattern

Answer 3

Anna where I can found that expression table.