1) Matrices can be defined as row vectors, column vectors, or 2D matrices in MATLAB. Common operations include addition, subtraction, multiplication, and exponentiation. 2) Predefined functions like ones, zeros, eye, and rand can be used to create matrices. Other functions like sum, diag, transpose, inv, and det perform operations on matrices. 3) Matrices can be concatenated horizontally using [A B] or vertically using [A;B]. Elements can be indexed and extracted from matrices using normal, linear, or logical indexing.