The Gamma conjectures was proposed by S. Galkin, V. Golyshev and H. Iritani and relate the quantum cohomology of a Fano manifold and the Gamma class in terms of differential equations. Gamma conjectures consist of conjecture $\mathcal O$, Gamma conjecture I and Gamma conjecture II. In this talk, we will introduce some basics about Gamma conjectures including Dubrovin conjecture, Gamma-integral structure and statement of Gamma conjectures. This talk is the first one of the series of talks on Gamma conjecture.