Regular Expression

Category	Symbol	Name	Meaning	Example	Matches
1. Wildcards & Character Classes
Matching Characters	(text)	Literal	Matches exact text	cat	"cat"
	.	Dot	Matches any single character (except newline)	h.t	"hat", "hot"
	[ ]	Brackets	List of allowed characters	b[ai]t	"bat", "bit"
	[^ ]	Negation	Matches anything NOT in the list	[^a]	Any char except 'a'
	\d	Digit	Any number 0-9	\d\d	"42", "99"
	\w	Word Char	Letter, number, or underscore	\w+	"User_1"
\s	Space	Whitespace (space, tab, enter)	A\sB	"A B"
2. Quantifiers (How Many?)
Counting	*	Star	0 or more times	go*d	"gd", "god"
	+	Plus	1 or more times	go+d	"god", "good"
	?	Question	0 or 1 time (Optional)	colou?r	"color", "colour"
	{n}	Exact Count	Matches exactly n times	\d{3}	"123"
	{n,}	Min Count	Matches n or more times	\d{3,}	"123", "12345"
	{n,m}	Range	Matches between n and m times	\d{2,4}	"12", "1234"
	.*?	Lazy Match	Matches as little as possible	<.*?>	Stops at first matching char
3. Anchors & Boundaries (Where?)
Positioning	^	Caret	Start of string/line	^The	Starts with "The"
	$	Dollar	End of string/line	end$	Ends with "end"
	\b	Word Boundary	The edge of a word (start or end)	\bcat\b	"cat" (not "scat")
4. Groups & Logic
Logic		Pipe	OR logic (Alternative)	dog	"cat" or "dog"
	(...)	Group	Groups characters or captures them	b)c	"ac" or "bc"
5. Special Characters
Escaping	\	Backslash	Treats special characters as text	\.	"." (actual dot)