A puzzle strongly related to mathematical facts and objects, or whose solution needs serious mathematical arguments. General mathematics questions are off-topic but can be asked on Mathematics Stack Exchange.
Mathematics (from Greek μάθημα máthēma = knowledge + study + learning) is the study of abstract topics as quantity, structure, space, and change. There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics.
Aristotle defined it as the science of quantity.
Auguste Comte defined it as the science of indirect measurement.
Bertrand Russell defined it as Symbolic Logic.
Walter Warwick Sawyer defined it as the classification and study of all possible patterns.
Wolfram MathWorld defines it as a broad-ranging field of study in which the properties and interactions of idealized objects are examined.
Mathematical puzzles make up an integral part of recreational mathematics. Mathematical puzzles require mathematics to solve them. Logic puzzles are a common type of mathematical puzzle.
Note that mathematical problems (as opposed to mathematical puzzles) are currently considered off-topic. See here for a discussion on the difference between the two. They might be welcomed on our sister site Mathematics Stack Exchange.