In mathematics, LHS is informal shorthand for the left-hand side of an equation.
The two sides have the same value, expressed differently, since equality is symmetric.
[1] More generally, these terms may apply to an inequation or inequality; the right-hand side is everything on the right side of a test operator in an expression, with LHS defined similarly.
For example in mathematical physics, the homogeneous equation may correspond to a physical theory formulated in empty space, while the inhomogeneous equation asks for more 'realistic' solutions with some matter, or charged particles.
More abstractly, when using infix notation the term T stands as the left-hand side and U as the right-hand side of the operator *.