In this talk, we will introduce the Hall algebra (and its spherical subalgebra) associated to the category of (parabolic) coherent sheaves on a smooth projective curve defined over a finite field and describe their structures in terms of shuffle algebras. We will then provide several applications in the context of quantum groups as well as on counting the Poincare polynomials of the moduli spaces of the stable (parabolic) Higgs bundles. If the time allows, we will discuss the position that Hall algebras play in the geometric Langlands program.