Kernel functions are used in machine learning including support vector machines to increase non-linear diversity. The term originates in mathematics where a postive definite kernel is a form of non-linear generalisation of the inner prooduct.
Used in glossary entries: machine learning, non-linear diversity, support vector machine
Links:
Wikipedia: Kernel method
Wikipedia: Positive definite kernel
turing.com: Designing of Different Kernels in Machine Learning and Deep Learning