Final answer:
Regular expressions are used to search, match, and manipulate strings. They consist of patterns and special characters that specify the search criteria. Common examples include patterns to match the start or end of a string, or to find all instances of a word in a sentence.
Step-by-step explanation:
Regular expressions examples:
To match a string that starts with 'cat': /^cat/
To match a string that ends with 'dog': /dog$/
To find all instances of the word 'apple' in a sentence: /apple/gi
Regular expressions are sequences of characters that define patterns for searching, matching, and manipulating strings. They are widely used in computer programming and text processing. In the examples above, the '^' and '$' symbols represent the start and end of a line or string, and the 'g' and 'i' flags stand for global and case-insensitive matching, respectively.