<p>I have worked for 5 years mainly in java desktop applications accessing Oracle databases and I have never used regular expressions. Now I enter Stack Overflow and I see a lot of questions about them; I feel like I missed something. </p>

<p>For what do you use regular expressions?</p>

<p>P.S. sorry for my bad english</p>

A regular expression (regex or regexp for short) is a special text string for describing a search pattern. You can think of regular expressions as wildcards on steroids. You are probably familiar with wildcard notations such as
```
*.txt
```
to find all text files in a file manager. The regex equivalent is
```
.*\.txt$
```
.
A great resource for regular expressions:
http://www.regular-expressions.info